فهرست مطالب

پژوهش های علوم دامی - سال بیست و هشتم شماره 3 (پاییز 1397)
  • سال بیست و هشتم شماره 3 (پاییز 1397)
  • تاریخ انتشار: 1397/09/10
  • تعداد عناوین: 13
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  • میلاد منافی *، مهدی هدایتی، هما آراک صفحات 1-16
    زمینه مطالعاتی
    کاهش مسمومیت ناشی از آفلاتوکسین در جوجه های گوشتی که به عنوان یکی از منابع تامین پروتئین انسانی هستند به واسطه به کارگیری ترکیبات گیاهی اهمیت دارد.
    هدف
    مطالعه حاضر به منظور بررسی اثرات عصاره های اتانولی آویشن شیرازی و پونه کوهی بر عملکرد، فراسنجه های بیوشیمیایی خون و ریخت شناسی روده باریک در جوجه های گوشتی تغذیه شده با جیره های غذایی آلوده به سم آفلاتوکسین B1 انجام شد.
    روش کار
    تعداد300 قطعه جوجه گوشتی )مخلوط نر و ماده (سویه تجاری راس 308 در قالب طرح پایه کاملا" تصادفی با 4 گروه آزمایشی و 5 تکرار (هر تکرار 15 قطعه جوجه گوشتی) مورد استفاده قرار گرفتند. گروه های آزمایشی عبارتند از: گروه اول: جیره پایه بدون آفلاتوکسینB1 (شاهد) ؛ گروه دوم: جیره پایه آلوده با آفلاتوکسین B1 به میزان 600 میکروگرم در کیلوگرم، گروه سوم: جیره شاهد به همراه مخلوطی از عصاره های اتانولی آویشن و پونه (هر کدام به میزان 500 میلی گرم در کیلوگرم) ؛ و گروه چهارم: جیره شاهد به همراه آفلاتوکسین B1 به میزان 600 میکروگرم در کیلوگرم و مخلوط عصاره های آویشن و پونه هر کدام به میزان500 میلی گرم در کیلوگرم.
    نتایج
    نتایج نشان داد که به کارگیری مخلوط عصاره های آویشن و پونه در جوجه های مبتلا به آفلاتوکسیکوزیس به طور معنی داری می تواند موجب بهبود وزن جوجه ها، کاهش ضریب تبدیل غذایی، افزایش ارتفاع ویلی ها و کاهش تعداد سلول های گابلت روده باریک نسبت به تیمار دریافت کننده سم گردد. هم چنین افزودن همزمان عصاره آویشن و پونه در جوجه های مبتلا به آفلاتوکسیکوزیس موجب کاهش مقادیر سرمی آلانین ترانس آمیناز، آسپاراتات ترانس آمیناز، آلکالین فسفاتاز، لیپوپروتئین با چگالی کم و لیپوپروتئین با چگالی بالا گردید.
    نتیجه گیری نهایی
    نتایج آزمایش حاضر نشان داد مکمل سازی جیره غذایی با عصاره گیاهی آویشن شیرازی و پونه کوهی سبب کاهش اثرات منفی آفلاتوکسین بر عملکرد، ساختار بافت شناسی روده و بهبود فراسنجه های بیوشیمیایی در جوجه های گوشتی می گردد.
    کلیدواژگان: آفلاتوکسینB1، عملکرد، ریخت شناسی روده، کلسترول، طول پرز
  • زهرا رحمتی مقدم، طاهره محمدآبادی* ، هدایت الله روشنفکر، مرتضی چاجی، خلیل میرزاده صفحات 17-29
    زمینه مطالعاتی:
    مغز بلوط حاوی 55 درصد نشاسته است که می توان از آن به عنوان منبع انرژی، در تغذیه دام نشخوار کننده در کنسانتره استفاده کرد.
    هدف
    هدف از این مطالعه، بررسی اثر جیره های آزمایشی حاوی سطوح صفر، 80/15، 58/31 و 37/47 درصد مغز میوه بلوط بر فراسنجه های تجزیه پذیری، تخمیری و قابلیت هضم آزمایشگاهی در گاو هلشتاین و گاومیش رودخانه ای خوزستان بود.
    روش کار
    میوه بلوط در سطوح صفر، 80/15، 58/31 و 37/47 درصد در جیره (تنظیم شده بر طبق جداول احتیاجات غذایی گاو) گاو و گاومیش استفاده شد. روش های تولید گاز، تلی و تری و کیسه گذاری شکمبه ای برای تعیین هضم، تخمیر و تجزیه پذیری این جیره های آزمایشی مورد استفاده قرار گرفت.
    نتایج
    میزان قابلیت هضم ماده خشک و NDF در گاو و گاومیش در تیمار حاوی 58/31 درصد مغز بلوط بالاترین مقدار بود (05/0P<). صرف نظر از نوع جیره آزمایشی، قابلیت هضم ماده خشک در گاو و گاومیش تفاوت معنی داری نداشت (05/0P>) ، اما قابلیت هضم NDF در گاومیش بالاتر از گاو (96/75 در برابر 53/65 درصد) بود (05/0P<). بدون توجه به نوع دام، بیشترین پتانسیل تولید گاز مربوط به تیمارهای حاوی مغز بلوط بود (05/0P<). مقدارPF ، تولید توده میکروبی، راندمان توده میکروبی و همچنین ماده آلی واقعا هضم شده بین جیره های حاوی مقادیر مختلف مغز بلوط متفاوت نبود (05/0P>). بخش کند تجزیه (b) ، پتانسیل تجزیه پذیری (PD) و تجزیه پذیری موثر (ED) در تیمار حاوی 58/31 درصد مغز بلوط در گاو و گاومیش بالاترین مقدار بدست آمد (05/0P<). بخش سریع تجزیه (a) ، بخش کند تجزیه (b) ، نرخ تجزیه (c) ، پتانسیل تجزیه پذیری (PD) و تجزیه پذیری موثر (ED) در گاو و گاومیش متفاوت نبود (05/0<P).
    نتیجه گیری نهایی
    با توجه به نتایج این آزمایش میتوان نتیجه گرفت که مغز میوه بلوط تا 58/31 درصد، به دلیل بهبود شرایط تخمیری شکمبه در شرایط آزمایشگاه، می تواند در جیره گاو هلشتاین و گاومیش خوزستانی استفاده شود اما در این زمینه نیاز به مطالعات بیشتری می باشد.
    کلیدواژگان: هضم پذیری، فراسنجه، تولید گاز، توده میکروبی
  • همایون فرهنگ فر*، سارا نظام دوست، محمدباقر منتظر تربتی، محمدرضا اصغری صفحات 31-46
    زمینه مطالعاتی
    با استفاده از مدل های مکانیستیک (زیست شناختی) می توان خصوصیات ژنتیکی منحنی شیردهی گاوها را از نقطه نظر بیولوژی ترشح شیر در بافت پستان، مورد بررسی قرار داد.
    هدف
    این تحقیق، با هدف استفاده از یک مدل مکانیستیک در ارزیابی خصوصیات ژنتیکی منحنی شیردهی گاوهای زینه (آمیخته) و اصیل هلشتاین اجرا گردید.
    روش کار
    از تعداد 1. 448. 292 رکورد شیر روز آزمون متعلق به 161. 676 راس گاو شیری (دختران 3. 979 راس گاو نر) در 921 گله که طی سال های 1376 تا 1391 برای نخستین بار زایش داشتند، استفاده شد. از مدل مکانیستیک پلوت - گوتوین با دو پارامتر MS (صفت مرتبط با حداکثر ظرفیت ترشح شیر) و DR (صفت مرتبط با کاهش نسبی تعداد سلول های ترشح کننده شیر) برای توصیف شکل منحنی شیردهی استفاده گردید. تابع غیرخطی فوق، بر داده های شیر روز آزمون هر گاو، به طور جداگانه برازش و پارامترهای آن برای هر یک از گاوها، برآورد شد. به منظور تخمین وراثت پذیری برای صفات MS و DR از مدل دام تک متغیره استفاده شد. روند ژنتیکی با روش تابعیت وزنی میانگین ارزش اصلاحی از سال زایش محاسبه گردید.
    نتایج
    وراثت پذیری MS و DR به ترتیب 293/0 و 190/0 بود. همبستگی پیرسون بین ارزش اصلاحی صفات مزبور 29/0- به دست آمد (0001/0P<). روندهای فنوتیپی و ژنتیکی برای MS به ترتیب 52/0 و 063/0 کیلوگرم در سال، و برای DR به ترتیب 000025/0- و 000007/0- و همه ی آن ها به لحاظ آماری معنی دار بودند (0001/0P<).
    نتیجه گیری نهایی
    با توجه به وراثت پذیری نسبتا بالا برای MS و DR ، درنظر گرفتن آن ها در شاخص انتخاب گاوها، می تواند منجر به بهبود ژنتیکی مناسبی برای صفات مزبور گردد.
    کلیدواژگان: روند ژنتیکی، گاوهای شیری، مدل مکانیستیک، منحنی شیردهی، وراثت پذیری
  • سمیرا سروری، علی حسین خانی* ، حمید محمدزاده ، اکبر تقی زاده صفحات 47-63
    زمینه مطالعاتی
    فرآوری حرارتی و نوع واریته دانه جو می تواند بر خصوصیات فیزیکی و تخمیری آن در شکمبه تاثیر بگذارد.
    هدف
    این آزمایش به منظور بررسی تاثیر واریته های دانه جو و طول مدت تفت دادن بر خصوصیات فیزیکی و تجزیه پذیری دانه جو انجام شد.
    روش کار
    دو واریته دانه جو (سهند و ماکویی) و چهار زمان فرآوری حرارتی (دمای 120 درجه سانتی گراد و زمان های0، 5،10، 15 دقیقه) در قالب طرح فاکتوریل 2*4 مورد بررسی قرار گرفتند. تجزیه پذیری شکمبه ای با استفاده از 2 راس گوسفند قزل فیستولادار و روش کیسه های نایلونی انجام پذیرفت.
    نتایج
    فرآوری حرارتی موجب کاهش تجزیه پذیری ماده خشک دانه جو در ساعات 16 تا 48 گردید. میزان تجزیه پذیری واریته سهند بیشتر از واریته ماکوئی بود بود (05/0P<). با این حال نوع واریته و تیمار حرارتی تاثیری بر میزان تجزیه پذیری دانه جودر ساعات اولیه انکوباسیون نداشتند. بخش با تجزیه پذیری سریع (a) و با تجزیه پذیری آهسته (b) و ثابت نرخ تجزیه (c) با تفت دادن در هر دو واریته کاهش یافت. چربی خام، حل پذیری ماده خشک و خاکستر، تحت تاثیر اثر ثابت واریته، ماده خشک تحت تاثیرزمان فرآوری و دیواره سلولی، دیواره سلولی منهای همی سلولز، ظرفیت نگهداری آب و جرم حجمی توده ای (BD100) تحت تاثیر اثرات ثابت زمان فرآوری و واریته قرار گرفتند. ظرفیت نگهداری آب دارای همبستگی مثبتی با ترکیبات دیواره سلولی (84/0r=) و دیواره سلولی منهای همی سلولز (71/0r=) بود. همچنین ارتباط بین BD100 با دیواره سلولی و دیواره سلولی منهای همی سلولز مثبت و به ترتیب (40/0r= و 35/0r=) بود.
    نتیجه گیری نهایی
    نتایج آزمایش نشان داد که با استفاده از واریته و فرآوری تفت دادن میتوان ضریب تجزیه پذیری ماده خشک دانه جو در شکمبه را کاهش داد.
    کلیدواژگان: غلات، ظرفیت نگهداری آب، جرم حجمی توده ای، فرآوری حرارتی
  • امیر کریمی*، ذبیح الله نعمتی صفحات 65-80
    زمینه مطالعاتی
    بررسی محدودیت شدید خوراکی دراثر کمبود ویا شرایط نوسانات قیمتی نهاده های خوراکی که می تواند تاثیر منفی بر رشد و بازده اقتصادی گله گوشتی داشته باشد.
    هدف
    این آزمایش به منظور بررسی اثر شدت محدودیت خوراکی در ابتدا و انتهای دوره پرورش جوجه های گوشتی بر عملکرد و شاخص آسیت انجام شده است.
    روش کار
    تعداد 1000 قطعه جوجه یکروزه سویه راس مخلوط نر و ماده در قالب طرح کاملا تصادفی به 8 گروه آزمایشی با 5 تکرار تقسیم شدند. گروه های آزمایشی عبارت بودند از: 1) گروه شاهد با جیره آزاد و کامل، 2) گروه 8 ساعت محدودیت خوراک روزانه از 9 تا 24 روزگی، 3) گروه 16 ساعت محدودیت از 9 تا 21 روزگی، 4) گروه 24 ساعت محدودیت (بصورت یک روز درمیان) از 9 تا 18 روزگی و سایر گروه های آزمایشی: 5) گروه10درصد محدودیت، 6) گروه 20 درصد محدودیت، 7) گروه 30 درصد محدودیت و 8) گروه 40 درصد محدودیت (از 22 تا 35 روزگی).
    نتایج
    بررسی های آماری نشان داد که گروه های دارای محدودیت خوراک 16 و 24 ساعت، در هفته سوم دارای مصرف خوراک و وزن بدن کمتر نسبت به گروه شاهد بوده اند (05/0>P) و مصرف خوراک و وزن بدن در گروههای 20، 30 و 40 درصد محدودیت در هفته چهارم نسبت به شاهد پایین تر بود (05/0>P) ، اما وزن این گروهها در هفته پنجم تفاوتی با گروه شاهد نداشت (05/0<P). در طول پرورش پایین ترین مصرف خوراک درگروه 24 ساعت محدودیت مشاهده شد (05/0>P) ؛ در حالیکه گروه 24 ساعت شاخص بازده تولید بالاتری داشت، اما تفاوت معنی داری بین گروه های آزمایشی، در رشد و وزن بدن، ضریب تبدیل خوراکی و شاخص بازده اروپایی مشاهده نشد (05/0<P) ؛ در انتهای دوره پرورش، هیچگونه تفاوت معنی داری بین گروههای آزمایشی در هماتوکریت و شاخص آسیت دیده نشد (05/0<P). تفاوت معنی داری بین گروههای آزمایشی درغلظت آنزیم کبدی لاکتات دهیدروژناز مشاهده نشد.
    نتیجه گیری نهایی
    بنظر می رسد با توجه به مصرف خوراک پایین تر و رشد جبرانی صورت پذیرفته و نیز شاخص اروپایی، گروه محدودیت 24 ساعت دارای عملکرد بهتری نسبت به سایر گروههای آزمایشی بوده است.
    کلیدواژگان: بازده تولید، رشد جبرانی، شاخص آسیت، محدودیت خوراکی
  • سعیده احمدی، محمدرضا شیخلو* ، صادق علیجانی صفحات 81-96
    زمینه مطالعاتی
    آمیزش افراد خویشاوند در جمعیت های بسته، کوچک و تحت انتخاب باعث بروز همخونی می گردد.
    هدف
    هدف از تحقیق حاضر بررسی روند همخونی و برآورد پسروی ناشی از آن در صفات وزن تولد، 3 ماهگی، 6 ماهگی، 9 ماهگی و یک سالگی در گوسفندان نژاد مغانی بود.
    روش کار
    ضریب همخونی دام ها با استفاده از اطلاعات شجره ای جمع آوری شده در مرکز اصلاح نژاد گوسفند مغانی برآورد گردید. سپس میزان افزایش همخونی فردی دام ها با استفاده از رابطه بین ضریب همخونی فرد و ضریب همخونی در نسل t برآورد گردید. از دو مدل که در یکی از آن ها ضریب همخونی و در دیگری افزایش همخونی فردی به عنوان متغیر کمکی در مدل منظور گردیده بود، جهت برآورد پسروی ناشی از همخونی استفاده گردید.
    نتایج
    میزان افزایش سالانه همخونی 03/0 درصد در سال برآورد گردید. میانگین وزن تولد و وزن 3 ماهگی دام های با همخونی بزرگتر از صفر و کمتر از ده درصد به طور معنی داری نسبت به دام های غیر همخون کمتر بود (05/0P<). با این وجود میانگین این صفات در دام های با همخونی بالای 10 درصد بیشتر از دیگر گروهها بوده و نسبت به حیوانات غیر همخون تفاوت معنی داری نداشت. ضریب تابعیت صفات وزن تولد، 3 ماهگی، 6 ماهگی، 9 ماهگی و یک سالگی از همخونی به ترتیب 6، 23-، 51-، 17- و 119- گرم و از افزایش همخونی فردی به ترتیب 22، 44-، 185- ، 111- و 326– گرم و غیر معنی دار بود. پس از تبدیل مقادیر افزایش همخونی فردی به معادل ضریب همخونی دامها، ضریب تابعیت صفات مورد بررسی از معادل ضریب همخونی به ترتیب 6، 13-، 55-، 33- و 96- گرم برآورد گردید.
    نتیجه گیری نهایی
    بر اساس نتایج این تحقیق آمیزش بین دام های خویشاوند باعث بوجود آمدن دام های همخون در گله شده بطوریکه بالغ بر 75 درصد گله دارای همخونی غیر صفر می باشد. از این رو بکارگیری روش هایی جهت کنترل افزایش همخونی در گله توصیه می گردد. در این تحقیق پاسخ پسروی ناشی از همخونی در صفات مختلف نسبت به بکارگیری افزایش همخونی فردی در مدل روند یکسانی نداشت.
    کلیدواژگان: افزایش همخونی فردی، پسروی ناشی از همخونی، گوسفند مغانی، صفات رشد
  • آرش داوریان، سعید خلجی، میلاد منافی ، مهدی هدایتی * صفحات 97-111
    زمینه مطالعاتی
    سنجد و گزنهدارای ترکیبات فعال زیادی می باشند که ممکن است بتوانند شاخص های عملکردی، کیفی و کمی تخم مرغ را تحت تاثیر قرار دهند.
    هدف
    این تحقیق جهت مقایسه اثر افزودن پودر میوه سنجد و پودر گزنه و مخلوط آن ها بر خصوصیات عملکردی، کیفی و کمی تخم مرغ در مرغان تخم گذار سویه های لاین W-36 در انتهای دوره تولید انجام پذیرفت.
    روش کار
    برای این آزمایش، از تعداد 128 قطعه مرغ تخم گذار نژاد لگهورن سفید، سویه های لاین W36 در سن 75 هفتگی در قالب طرح کاملا تصادفی با اندازه گیری های تکرار شونده در زمان با 4 گروه آزمایشی، 8 تکرار و 4 مشاهده در هر تکرار و در سه دوره بیست و یک روزه آزمایشی (جمعا 63 روز) جهت ارزیابی تاثیر میوه سنجد و پودر گزنه و مخلوط هر دو بر خصوصیات کیفی و کمی تخم مرغ مورد بررسی قرار گرفت. گروه های آزمایشی شامل شاهد، 1 درصد پودر گزنه 1 درصد پودرمیوه سنجد و 5/0 درصد پودر گزنه و 5/0 درصد پودر میوه سنجد بودند. در پایان هر دوره آزمایشی، از هر تکرار یک عدد تخم مرغ به صورت تصادفی، انتخاب و پس از شماره گذاری، پارامترهای مربوط به کیفیت داخلی آن ها اندازه گیری شد.
    نتایج
    گروه آزمایشی حاوی میوه سنجد بر ارتفاع سفیده و واحد هاو اثر معنی داری داشت (05/0P<) و دوره آزمایشی دوم نیز اثر معنی داری بر ارتفاع سفیده، واحد هاو و دوره آزمایشی سوم هم تاثیر معنی داری بر رنگ زرده تخم مرغ از خود نشان داد (05/0P<). همچنین گروه ها و دوره های آزمایشی تاثیر معنی داری از لحاظ آماری بر پارامترهای عملکردی نداشتند (05/0<P).
    نتیجه گیری نهایی
    نتایج مطالعه حاضر نشان داد که مصرف پودر سنجد در سطح 1 درصد مقدار واحد هاو و ارتفاع سفیده تخم مرغ را افزایش می دهد.
    کلیدواژگان: تخم مرغ، سنجد، فراسنجه های عملکردی، فراسنجه های کیفی، گزنه، مرغ تخم گذار
  • جمال فیاضی، عباس مسعودی، رستم عبداللهی آرپناهی ، آذر راشدی ده صحرائی* صفحات 113-126
    زمینه مطالعاتی
    مدل‏های رشد، توابع ریاضی هستند که برای توصیف الگوی رشد به کار می‏روند.
    هدف
    هدف از انجام این پژوهش، برآورد فراسنجه های ژنتیکی پارامترهای رشد حاصل از بهترین مدل غیرخطی و عوامل محیطی مختلف موثر بر این پارامترها در گوسفندان مغانی بود.
    روش کار
    در این پژوهش، به منظور برآورد اجزاء (کو) واریانس پارامترهای الگوی رشد، از تعداد 7278 رکورد وزن تولد، 5881 رکورد وزن شیرگیری، 5013 رکورد وزن شش ماهگی، 2819 رکورد وزن نه ماهگی و 2883 رکورد وزن یک سالگی گوسفندان مغانی که طی سال های 1374 تا 1389 در ایستگاه پرورش و اصلاح نژاد این گوسفند واقع در جعفرآباد مغان جمع آوری شده بود، استفاده شد. در این مطالعه پارامترهای الگوی رشد (وزن بلوغ، نرخ رشد و نرخ بلوغ) با استفاده از چهار مدل رگرسیون غیرخطی گومپرتز، لجستیک، برودی و ون برتالانفی با رویه NLIN نرم افزار SAS محاسبه شد. جهت برآورد اجزای واریانس-کواریانس پارامترهای الگوی رشد از روش آماری بیزی مبتنی بر تکنیک نمونه گیری گیبس و نرم افزار MTGSAM استفاده شد.
    نتایج
    مدل ون برتالانفی به علت داشتن بیشترین ضریب تبیین و کمترین مقدار آکائیکی به عنوان مدل برتر در مقایسه با سایر مدل ها، انتخاب شد. عوامل محیطی سال تولد (01/0P<) ، جنسیت بره (01/0P<) و سن مادر هنگام زایش (05/0P<) بر وزن بلوغ و نرخ رشد از لحاظ آماری معنی دار بودند. اثرات ثابت سال تولد و جنسیت بره بر نرخ بلوغ اثر معنی دار داشتند (01/0P<). از بین شش مدل خطی برازش شده در روش بیزی، بر اساس کمترین مقدار واریانس باقیمانده برای وزن بلوغ مدل 4، برای نرخ رشد مدل 6 و برای نرخ بلوغ مدل 5 انتخاب گردید. وراثت پذیری مستقیم برآورد شده بر اساس مدل مناسب انتخاب شده، برای صفات مذکور به ترتیب برابر 003/0±29/0، 004/0±35/0 و 005/0±21/0 بود. همبستگی بین پارامترهای الگوی رشد مثبت و نزدیک به صفر برآورد شد.
    نتیجه گیری کلی
    طبق نتایج به دست آمده، اثر عوامل محیطی بر پارامترهای الگوی رشد مهم و تاثیرگذار هستند و باید در تجزیه و تحلیل این پارامترها مورد بررسی قرار گیرند.
    کلیدواژگان: الگوی رشد، توابع غیرخطی، روش بیزی، گوسفند مغانی
  • فاطمه شاهوردی، محمود وطن خواه ، عبدالاحد شادپرور * صفحات 127-138
    زمینه مطالعاتی
    یکی از برنامه های اصلاح نژادی گوسفند طرح اصلاح نژادی دارای هسته است. نتایج این طرحها ممکن است تحت تاثیر اندازه هسته و شدت انتخاب قرار بگیرند.
    هدف
    بررسی اثر اندازه هسته به صورت نسبتی از کل جمعیت در سه سطح 5، 10 و 15 درصد و شدت انتخاب نر ها و ماده ها در سه سطح شدید، متوسط و ضعیف بر میزان اریبی در برآورد پیشرفت ژنتیکی ناشی از نادیده گرفتن اثر کاهشی انتخاب بر واریانس ژنتیکی افزایشی صفت.
    روش کار
    دراین پژوهش یک طرح اصلاح نژاد هسته باز با استفاده از اطلاعات جمعیت گوسفندان نژاد لری بختیاری مرکب از یک هسته با 1005 راس و یک پایه با 4019 راس میش مولد به روش شبیه سازی قطعی تعریف شد. صفت تابع هدف، وزن تولد و انتخاب بر اساس یک رکورد شخصی بود.
    نتایج
    با افزایش اندازه نسبی هسته از 5 به 15 درصد، میزان اریبی از 84/11 تا 67/16 افزایش یافت. در اثر افزایش شدت انتخاب از ضعیف به شدید، میزان اریبی از 18/14 به 72/17 تغییر کرد. با تغییر نرخ انتقال قوچ از هسته به پایه رشد ژنتیکی به صورت غیر خطی تغییر کرد و در یک نقطه خاص به حداکثر رسید که نقطه بهینه نامیده می شود. این نقطه بهینه در شرایط مختلف بین 50 تا 75 درصد تغییر کرد و مستقل از اثر انتخاب بود. در نرخ های انتقال بهینه، میزان اریبی حداقل بود. بررسی اثر همزمان اندازه هسته و شدت انتخاب نشان داد که در شدت انتخاب های بالا، هنگامی که اندازه هسته از 10 درصد بیشتر بود، میزان اریبی به میزان بسیار اندک تحت تاثیراندازه هسته قرار گرفت.
    نتیجه گیری نهایی
    نتایج این تحقیق نشان داد در شدت انتخاب ضعیف، می توان با نادیده گرفتن اثر انتخاب، برنامه بهبود ژنتیکی را بهینه سازی کرد. در شدت انتخاب شدید نادیده گرفتن این اثر می تواند منجر به نتیجه گیری اشتباه شود.
    کلیدواژگان: تاخیر ژنتیکی، شبیه سازی قطعی، گوسفند لری بختیاری، واریانس ژنتیکی
  • شهریار کارگر ، فاطمه فتحی* صفحات 139-152
    زمینه مطالعاتی
    توجه به مقوله ی سلامت انسان از طریق مصرف محصولات غذایی سالم و با کیفیت از مهمترین مسائل مورد بحث در زندگی بشر است. شیر فراسودمند به عنوان محصول لبنی در دسترس می تواند در پیشگیری از سرطان و سکته های قلبی-عروقی نقش داشته باشد.
    هدف
    در این پژوهش عوامل موثر بر مصرف شیر فراسودمند و تمایل به پرداخت مصرف کنندگان در شهر شیراز بررسی شد.
    روش کار
    این پژوهش با تکمیل 279 پرسش نامه به روش تصادفی از خانوارهای شهر شیراز و با استفاده از برآورد مدل دو مرحله ای هکمن انجام شد.
    نتایج
    بهداشتی بودن و کیفیت شیر (فراسودمند بودن) مهم ترین عوامل تاثیرگذار در افزایش تقاضای شیر بودند و تمایل به پرداخت شیر فراسودمند 19 درصد بیش تر از قیمت شیر کم چرب موجود در بازار برآورد شد.
    نتیجه گیری کلی
    به دلیل مزیت نسبی شیر فراسودمند نسبت به شیر معمولی و تمایل به پرداخت بیشتر مصرف کنندگان، تولید صنعتی شیر فراسودمند در مزارع پرورش گاو شیری با توجه به هزینه های سر باری که می تواند داشته باشد از دیدگاه تولیدکننده قابل توجیه می گردد.
  • محمد قهرمان زاده* ، قادر دشتی، رضا پهلوانی، فاطمه ثانی صفحات 153-168
    زمینه مطالعاتی
    پرورش دام سبک یکی از مهم ترین و با سابقه ترین فعالیت های بخش کشاورزی است. در کشور ما دو سامانه روستایی و عشایری برای پرورش دام سبک وجود دارد. در طی سال های گذشته تلاش های زیادی از سوی دولت برای بهبود وضعیت بهره وری این دو سامانه صورت گرفته است.
    هدف
    مطالعه حاضر با هدف بررسی و مقایسه میزان تاثیر سیاست های حمایتی دولت بر بهره وری کل عوامل تولید در این دو سامانه، طی سال های 92- 1376 در چهار استان منتخب کشور شامل لرستان، کرمانشاه، همدان و ایلام انجام گردیده است.
    روش کار
    میزان حمایت های دولت براساس شاخص های سازمان توسعه و همکاری های اقتصادی (OECD) و میزان بهره وری کل عوامل تولید براساس شاخص دیویژیا محاسبه گردید. برای تعیین رابطه هم جمعی بین متغیرهای تحقیق از آزمون پدرونی استفاده گردید و رابطه تعادلی بلندمدت از طریق روش گشتاورهای تعمیم یافته (GMM) برآورد شد.
    نتایج
    نتایج نشان داد حساسیت بهره وری کل عوامل تولید (TFP) نسبت به شاخص حمایت از تولیدکننده (PSE) ، در سامانه عشایری از سامانه روستایی بیشتر است. علت این برتری را می توان در ویژگی های این سامانه هم چون هزینه های ثابت و متغیر کمتر، استفاده بیشتر از زمان رشد، مدیریت متمرکز، تخصص گرایی توسط فعالان این سامانه و غیره دانست.
    نتیجه گیری نهایی
    براساس نتایج این تحقیق پیشنهاد می گردد تا از تلفیق دو سامانه، سامانه جدیدی تحت عنوان کوچ تابستانه شکل گیرد. در این شیوه تولید به دلیل وجود ضرایب تولید مثلی بالاتر، تولید گوشت و لبنیات بیشتر و نیز هزینه کمتر، بهره وری و بازدهی تولید بیشتر خواهد بود. بدیهی است نتایج این تحقیق می تواند ضمن هدفمند نمودن سیاست های حمایتی دولت به افزایش بهره وری عوامل تولید در این رشته فعالیت و در نهایت افزایش ثروت و سرمایه ملی کمک نماید.
    کلیدواژگان: بهره وری کل عوامل تولید، داده های ترکیبی، دام سبک، روش گشتاورهای تعمیم یافته (GMM)، سیاست های حمایتی دولت
  • شهروز بصیری، وحدت طاهری ، وحید عطاری * صفحات 169-179
    زمینه مطالعاتی
    این مطالعه به منظور بررسی اثر مخلوط گیاهان شیر افزا بر تولید شیر و سطح پرولاکتین و هورمون رشد در گاوهای شیرده هلشتاین انجام شد.
    هدف
    این آزمایش در قالب طرح کاملا تصادفی با 12 راس گاو شیرده هلشتاین با میانگین وزن 15±620 کیلوگرم، میانگین روز شیردهی 10±30 روز و میانگین تولید شیر10±33 کیلوگرم در روز انجام شد.
    روش کار
    در این مطالعه گاوها به دو گروه تقسیم شدند، گروه اول (6 راس) به عنوان گروه شاهد که با جیره ی پایه تنظیم شده براساس احتیاجات غذایی NRC (2001) برای تامین احتیاجات گاوهای شیری تغذیه شد و گروه دوم (6 راس) که همراه با جیره پایه پودر گیاهان دارویی شیرافزا (03/0 درصد وزن بدن) (شامل مخلوط دانه رازیانه، سیاه دانه و زیره سیاه) به صورت مخلوط با کنسانتره استفاده شد. دوره اصلی به مدت 8 هفته پس از یک هفته دوره عادت دهی اجرا شد. در این مدت شیر تولیدی دام ها هر دو روز یکبار اندازه گیری و ثبت شده و ترکیبات آن تعیین شد. در انتهای آزمایش از تمامی دام ها از طریق ورید وداجی خونگیری شده و به منظور تعیین میزان هورمون رشد و پرولاکتین به آزمایشگاه انتقال یافت.
    نتایج
    نتایج نشان داد که تولید شیر دام های تغذیه شده با تیمار شیرافزا افزایش معنی داری (0001/0>(P داشته است (3/36 کیلوگرم در مقابل8/33 کیلوگرم). درصد ترکیبات شیر تغییر معنی داری نشان نداد، هر چند مقادیر تولید روزانه آنها در پاسخ به افزایش شیر تولیدی به طور معنی دار (05/0P<) شد. سطوح هورمون رشدو پرولاکتین نیز، تمایل به افزایش نشان داد که از لحاظ آماری معنی دار نبود.
    نتیجه گیری نهایی
    می توان نتیجه گرفت که استفاده از این ترکیب گیاهان شیرافزا در بهبود تولید شیر می تواند موثر باشد.
    کلیدواژگان: تولید شیر، پرولاکتین، گاو هلشتاین، گیاهان شیرافزا، هورمون رشد
  • مسعود علیخانی، احمد ریاسی، غلامرضا قربانی ، احمد شاهمرادی * صفحات 181-193
    زمینه مطالعاتی
    به منظور بررسی اثر استفاده از مواد خوراکی لیپوژنیک در مقایسه با گلوکوژنیک در گاوهای هلشتاین بر خوراک مصرفی، عملکرد تولیدی و pH شکمبه ای در دوره انتقال، 24 راس گاو هلشتاین چند شکم زایش (1 تا 3 شکم زایش) مورد آزمایش قرار گرفتند.
    روش کار
    گاوها بر اساس شکم زایش بلوک بندی شده و بصورت تصادفی به سه تیمار تقسیم بندی شدند. تیمارها بترتیب در قبل از زایش به شرح زیر بودند: 1)100 درصد جو بعنوان منبع غله در کنسانتره (بدون تفاله چغندرقند، جیره گلوکوژنیک) ، 2)75 درصد جو بعنوان منبع غله (به همراه 25 درصد تفاله چغندرقند، جیره لیپوژنیک پایین) و 3)50 درصد جو بعنوان منبع غله (به همراه 50 درصد تفاله چغندرقند، جیره لیپوژنیک بالا) که این درصدها در پس از زایش نیز رعایت شدند.
    نتایج
    خوراک مصرفی و انرژی مصرفی روزانه در قبل و بعد از زایش در تیمار لیپوژنیک پایین بیشترین بود (01/0P<). خوراک مصرفی بر اساس درصد وزن بدن در قبل از زایش با افزایش سطح تفاله چغندرقند در جیره ها افزایش یافت و در پس از زایش نیز در تیمار لیپوژنیک پایین بیشترین بود (01/0P<). در تیمار لیپوژنیک بالا تولید شیر، درصد و تولید پروتئین شیر کاهش ولی درصد چربی شیر افزایش یافت (01/0P<). تولید لاکتوز شیر در تیمار لیپوژنیک بالا کمترین بود (05/0P<). pH شکمبه در پس از زایش در تیمار گلوکوژنیک پایین ترین بود (05/0P<).
    نتیجه گیری نهایی
    باتوجه به نتایج این آزمایش بنظر می رسد با جایگزینی 25 درصد تفاله چغندر قند با جو (جیره لیپوژنیک پایین) در جیره های دوره انتقال می توانیم عملکرد بهتر و سلامت شکمبه ای بیشتری در این دوره داشته باشیم.
    کلیدواژگان: دوره انتقال، تفاله چغندرقند، دانه جو، گلوکوژنیک و لیپوژنیک
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  • M Manafi *, M Hedayati, H Arak Pages 1-16
    Introduction
    Aflatoxins are a class of secondary metabolites of fungi, which are present in the form of B (B1 and B2), G (G1 and G2), and M (M1 and M2) and are distinguished from each other through chromatography and fluorescent light. Aflatoxin B1 is more abundant in the feedstuff and more toxic than all other types of toxins (Manafi et al. 2011). Aflatoxins are the result of the metabolic activity of Aspergillus fungi, and in particular Aspergillus flavus, which can cause food contamination of living creatures. Aflatoxicosis has caused severe economic losses in the poultry industry and has had a negative impact on duck, broilers, laying hens, turkeys and quails (Deabes et al. 2011). The sensitivity of chickens to aflatoxin negative effects depends on a wide range of factors such as breed, aflatoxin concentration, age, nutritional status, as well as the capacity of liver microsomal enzymes to decontaminate aflatoxin. Mycotoxins normally affect intestinal secretions. The use of aflatoxin is proven to reduce the production of pancreatic secretions and changes in the intestinal morphology (the depth of the intestinal crypts), and the special activity of disaccharide and maltase in broiler’s intestine (Applegate et al. 2009). Increasing free radical formation or reducing the level of antioxidants in the body through aflatoxicosis leads to oxidative stress, which can lead to tissue destruction through the physical, chemical and physiological conditions (Eralsan et al. 2005). Reducing the toxicity of aflatoxin in broiler chickens as an important source of animal-based proteins for human beings by utilizing a combination of plant derivatives is considered vital. It has been suggested that the antioxidant properties of essential oils and plant extracts due to the presence of phenolic groups as a hydrogen supplier to peroxide radicals produced during oxidative stress, which will delay or deny peroxide formation (Roquia 2012).
    Materials and method
    The current experiment is designed in order to study effects of ethanolic extractions of thyme and oregano on performance, blood biochemical parameters and small intestinal properties of broilers fed diets contaminated with aflatoxin B1. The total number of 300 Ross 308 chicks (mixed sex) were used in completely randomized design with 4 treatments and 5 replicates with 15 birds in each replicate. Treatments consisted of: 1- basal diet without aflatoxin B1 (control); 2- Basal diet with Aflatoxin group (basal diet + 600 ppb aflatoxin B1); 3- Basal diet with mixture of ethanolic extraction of thyme and oregano (either 500 ppm) and 4- Basal diet with Aflatoxin + mixture of ethanolic extraction of thyme and oregano (either 500 ppm). In the current study, performance including mortality, feed intake, and weight of birds were recorded weekly till the end of the rearing period. At the end of production period, from each experimental unit, 2 birds were selected and after killing by humanized method, sampling for intestinal morphology from the ileum part (with a distance of 2 cm from Meckl's appendix) with the length of 5 cm was done. Also, in order to check the blood parameters from each experimental group, two birds were randomly selected and blood samples were collected. Then, blood biochemical parameters included liver enzymes (ALT, AST and ALP), triglycerides, cholesterol, LDL and HDL were measured using the Pars Azmon Company kits and the Autoanalyzer apparatus (US, Technicon RA-1000). Aflatoxin B1 was purchased from Sigma Aldrich Company and was prepared according to the manufacturer's instructions for the preparation of the poison. Six mg of poison was mixed with 100 cc of 96% ethanol and then, sprayed on 1 kg of feed to obtain a homogeneous mixture of aflatoxin B1 contaminated feed. Ethanolic extracts of thyme and oregano were prepared by the Macceration method in the laboratory of the Department of Animal Science, Malayer University. The data obtained from this experiment were analyzed by SAS software. Mean comparison was done using Duncan's multiple -domain test at 5% error level.
    Results and discussion
    The results of the experiment showed that the weight of birds receiving aflatoxin B1 contaminated rations were reduced compared to the control group (P<0.05). Weight gain of broiler chicks in the experimental group receiving aflatoxin with a mixture of thyme and oregano extract increased compared to the experimental group receiving aflatoxin alone in the diet (P<0.05). This is in accordance with the reports of Manafi et al. (2009) who showed that consumption of one mg per kilogram of aflatoxin reduced the yield and growth of broiler chickens up to 5 percent. Decreased feed intake and impaired metabolism of energy and fat due to the use of aflatoxin in the diet due to changes in taste and disturbance in digestion and absorption mechanisms have been reported in various studies (Raju and Devegowda 2002). The presence of mannan oligosaccharide compounds and antioxidant compounds in thyme and oregano such as thymol and carvacrol may have antioxidant properties against negative activity of aflatoxin and inhibitory effects on metabolic changes caused by aflatoxin such as liver toxicity and contribute to reducing weight gain in broilers (Burt, 2004). A mixture of thyme and oregano extracts, and the consumption of feed in the experimental group receiving aflatoxin in comparison to the control group showed a significant decrease. Addition of plant extracts to aflatoxin contaminated diets increased significantly feed intake compared with control group (P<0.05). The increased in feed intake is due to the addition of herbal extracts. Thyme have appetitive factors like thymol and carracorol and other growth factors, which stimulates digestive enzymes and increases daily feed intake of broiler chickens (Cabuk et al. 2006). The group receiving herbal extracts in the 6th week had a lower FCR than the control group and the aflatoxin received group (P<0.05). Cinnamon-containing compounds and Thymol and Carvacrol have probably a role in improving the chicken feed conversion rate (Cabuk et al. 2006). Also addition of thyme and oregano extracts in aflatoxin challenged broilers caused a significant decrease in ALT, AST, ALP, LDL, and HDL (P<0.05). This might be due to the antioxidant properties of two plants, which reduce the toxic effects of oxidative toxicity on the liver and reduce cholesterol, triglyceride and liver enzymes. The reason for this decrease is the inhibitory effects of these extracts on the action of key enzymes such as HMG-COA reductase, which is present in the production of lipids and cholesterol (Sarica et al. 2005). Chickens receiving thyme and oregano extract had the highest villus height and showed a significant differences in comparison with other experimental groups (P<0.05). The villus height to crypt depth ratio was the highest in the group receiving the herbal extracts and the lowest amount was observed in the group receiving the aflatoxin and the addition of herbal extract to the contaminated diet improved this index significantly (P<0.05). Increasing the crypt depth in the ileum region and reducing digestion and absorption in this region might be due to the damage in the intestinal mucosal tissues of chickens fed contaminated diets.
    Conclusions
    The results obtained from this research states that dietary supplementation with plant extracts of thyme and oregano reduces the negative effects of aflatoxin on performance, gastrointestinal index and improves the biochemical parameters in broiler chickens challenged with aflatoxicosis.
    Keywords: Aflatoxin B1, Broilers, Herbal extracts, Intestinal morphology, Performance
  • Z Rahmati, T Mohammadabadi *, H Roshanfekr, M Chaji, Kh Mirzadeh Pages 17-29
    Introduction
    Oak kernel contains high starch, so it can be used as an energy source in the concentrate of ruminant diet. Also, oak kernel containing active biological compounds, such as tannin, gallic acid, galloyl or hexahydroxy decanol derivatives (Saffarzadeh et al. 1999). Tannins form complexes with a large number of nutrients and bacterial cell membranes, enzymes, and decrease digestion in the rumen (Rajablo 2009). The aim of this study was to investigate the effect experimental diets including 0, 15.80, 31.58, and 47.37% oak kernel on degradability parameters, fermentative and in vitro digestibility in Holstein cow and river Khuzestani buffalo.
    Material and methods
    Oak kernel used by 15.8, 31.58 and 47.37 % in diet (balanced on the base of NRC, 2001) of cow and buffalo. Gas production and fermentation parameters of experimental diets were determined by Menke and Steingass (1988). Rumen fluid was collected from animals before the morning feeding. About 200 mg sample (1.0 mm screen) incubated in 100 ml vials with 35 ml buffered rumen fluid under continuous CO2 reflux for 2, 4, 6, 8, 10, 12, 16, 24, 48, 72 and 96 h, in a water bath maintained at 39°C. Cumulative gas production data were fitted to the exponential equation Y=b (1−e−ct), where b is the gas production (mL) from the fermentable fraction, c is the rate constant of gas production (mL/h), t is the incubation time (h) and Y is the volume of gas produced at time t. Partitioning factor, microbial biomass and truly digested organic matter was calculated by Makkar and Becker (1997). For determination of partitioning factor at the end of each incubation period, the content of vials was transferred into an Erlenmeyer flask, mixed with 20 mL neutral detergent fiber solution, boiled for 1 hour, filtered, dried (in oven at 60 °C for 48 h) and ashed. Digestibility of dry matter and NDF of experimental diets were determined using Tilly and Terry method (Tilly and Terry 1963). Rumen fluid was collected from animals and was mixed with McDougall buffer in a ratio 1:4. After gasifying with CO2, tubes were incubated at 39 ˚C. After 48 h of fermentation, 6 mL of 20% HCl solution and 5 mL pepsin solution were added and the incubated for 48 h simulating post-ruminal degradation. After incubation, the residual substrates of each tube were filtered and used to determine digestibility of DM and NDF.
    Dry matter degradability was measured by in situ technique using cow and buffalo fitted with rumen fistula (400±12 Kg, BW). Five g of each milled sample (2.0 mm screen) were transferred into a polyester bag (10×20 cm, 52 μm pore size) and incubated in the rumen for 2, 4, 6, 8, 16, 24, 4 8, 72 and 96 hours (n= 4). The degradability of DM were calculated using the equation P = a + b (1- e -ct). The obtained data were analyzed in a split plot design using the General Linear Model (GLM) procedure of SAS software, version 9.2. The Duncan multiple range test was used to compare means at P< 0.05.
    Results and discussion
    Dry matter digestibility and NDF were the highest in treatment including 31.58% oak kernel in cow and buffalo (P<0.05). Regardless of the type of treatment, dry matter digestibility was not significant in cow and buffalo (P>0.05), but NDF digestibility in buffalo was more than cows (P<0.05). The highest potential of gas production was for diets containing oak kernel (P<0.05). The value of PF, microbial biomass, microbial biomass efficiency and organic matter digested was not significant between diets containing different amounts of oak kernel (P>0.05). Slowly degradable fraction (b), potential of degradability (PD) and effective degradability (ED) were the highest in the diet containing 31.58% oak kernel (P<0.05). Fraction of rapidly degradable (a), slowly degradable fraction (b), constant degradable rate (c), potential of degradability (PD) and effective degradability (ED) was not different in cow and buffalo (P>0.05). Researchers reported that tannins cause inhibition of microbial enzymes and decrease in fermentation (Danesh Mesgaran 2009). Tannins can reduce microorganism adhesion to nutrients; inhibit microbial activity which has negative effects on fermentation and methane production (Frutos 2004).
    Conclusion
    According to the result, it can be concluded, 31.58% oak kernel by improving in vitro fermentative condition of rumen can be used in diet of cow and Khuzestan buffalo, but it requires more studies.
    Keywords: Digestibility, Gas production, Microbial biomass, Parameter
  • H Farhangfar*, S Nezamdoust, MB Montazer, MR Asgari Pages 31-46
    Introduction
    Successful animal breeding strategies rely on selecting superior animals to produce progeny which are expected to have better performance compared to contemporaries at different rearing environments (Doeschl-Wilson 2007). Based on this, the main aim of a breeding scheme is to promote genetic potential of livestock for the traits of great economic importance. Milk yield varies over a course of lactation as a result of continuous physiological mechanisms of growth and death of udder cells (Val-Arreola 2004). Mathematical models used for description of the lactation curve can be empirical (shape-oriented) or mechanistic (biology-oriented) (Farhangfar 2015). Using mechanistic (biological) models it would be possible to study genetic aspects of cows' lactation curve from the biology of milk secretion in udder tissue standpoint. Vast majority of the research undertaken on the lactation curve of Iranian dairy cows have been focused on the use of empirical models. This research was carried out with the objective of evaluating genetic characteristics of the lactation curve of Iranian Holstein grade and pure-bred dairy cows using a mechanistic model.
    Material and methods
    The data used in this research were provided by Animal Breeding Centre, Karaj, Iran. The data set consisted of 1,448,292 test day milk records belonging to 161,676 first parity cows (progeny of 3979 bulls) in 921 herds (in 14 provinces over the country) and calved during 1997- 2012. Minimum and maximum number of test day records were 4 and 13, respectively. Based on the percentage of Holstein gene inheritance (H), cows were divided into four groups. Pollott-Gootwine mechanistic model with two parameters of MS (maximum secretion potential of the lactation) and DR (relative decline in cell numbers) was applied to describe the shape of lactation curve. This nonlinear function was fitted to the individual lactation curves and the parameters were estimated for each cow by using nonlinear procedure of SAS software. Heritability of MS and DR traits was estimated using a fitting univariate animal model. In the model, effects of province, contemporary group of herd-year-season, calving age, type of genotype, interval of first test day from calving, fat to protein ratio, length of lactation as well as random effect of cow were included. All relationship among the animals were taken into account through including pedigree. The model was run for each trait using DMU software and restricted maximum likelihood (REML) estimate of additive genetic and residual variance components and prediction of breeding value of the animals were obtained. Genetic trend was subsequently calculated through fitting weighted regression of mean breeding value on calving year.
    Results and discussion
    Additive genetic and residual variance components for MS were 5.7123 and 13.7759, respectively and the corresponding figures for DR were 0.0000012 and 0.0000051, respectively. Heritabilities of MS and DR were found to be 0.293 (SE=0.008) and 0.194 (SE=0.120), respectively indicating that there is relatively good genetic variation for the traits to be used in selection programmes. Mean predicted breeding value (PBV) of the cows with records were 0.255 (Kg) and -0.000005 for MS and DR, respectively. Regarding MS, cows with 50  H  75 had minimum PBV (0.072 Kg) while cows with 87.5  H 100 had maximum PBV (0.309 Kg) and the difference was statistically significant (P<0.05). Based upon mean PBV for MS, mean PBV for the trait of 305-day milk yield in pure-bred Holstein cows (H=100) was expected to be 82.96 Kg. Pearson correlation between breeding values of the traits was -0.29 (P<0.0001) suggesting that cows of high genetic potential for MS are expected to have low breeding value for DR. Phenotypic and genetic trends for MS were 0.52 (SE=0.017) and 0.063 (SE=0.004, R2=0.95) kg per year, respectively, while the corresponding figures for DR were -0.000025 (SE=0.0000021) and -0.000007 (SE=0.00000054, R2=0.92), respectively and that all the trends were statistically significant (P<0.0001).
    Conclusion
    High heritability of MS and DR suggests that appropriate genetic gain could be obtained as the selection of the cows is based upon these traits. As DR is associated with lactation persistency, it could be therefore concluded that Iranian dairy cows have become phenotypically and genetically persistent over the years of 1997-2012.
    Keywords: Dairy cows, Genetic trend, Heritability, Lactation curve, Mechanistic model
  • S Sarvari, A Taghizadeh, H Mohammadzadeh, A Hoseinkhani* Pages 47-63
    Introduction
    Barley grain is one of the major feedstuff in ruminant animal’s nutrition due to its high energy density and lower price than grains such as corn. Rate of barley starch digestion in the rumen is critical issue in high-grain fed ruminants because it is associated with higher performance of animal. Feeding high amount of barley in ruminant animal rations can cause an increase in the incidence of digestive disorders including reduced feed intake, off-feed, acidosis, and liver abscesses. Processing methods such heat treatment can affect physical characteristics and ruminal fermentation of grain. Moreover, barley grains from diverse cultivars are different in their chemical composition and fermentation characteristics due to geographical, environmental and genetic variations as well as their interactions. This experiment was conducted to investigate the effects of variety and heat treatment duration on physical characteristics and ruminal disappearance of barley grain.
    Material and methods
    Two varieties of endemic barley grain (i.e. Sahand and Makoei) were prepared from Seed and Plant Improvement Institute, Karaj, Iran. The grains were roasted in three time duration (5, 10 or 15 min at 120o C) in a cast iron container. The experiment was conducted using a 2*3 factorial design. The samples were dried in 60° oven for 48 hours. Chemical composition was determined according to prescribed procedures of AOAC (2002). Neutral detergent finer (NDF) and acid detergent fiber (ADF) were measured by method of Van-Soest et al. (1991). Bulk density of sample was determined using the method described by Montgomery and Baumgardt (1965). Water holding capacity (WHC) determined by filtration method (Robertson and Eastwood, 1981). Dry matter solubility and ash solubility of samples were determind by method of Giger-Reverdin (2000). Dry matter degradability was measured by in situ technique using two fistulated Ghezel sheep (fed 60% forage + 40% concentrate). Samples were put in the polyester bags and incubated in the rumen for 2, 4, 8, 12, 16, 24, 36, and hours. After the specific incubation periods, bags were washed under running tap water until the effluent was clear and then dried at 55◦C for 48 h. Bags and contents were weighed to estimate DM disappearance (DMD). Kinetic parameters of DM degradation was estimated by the nonlinear regression procedure of SAS (SAS Inst. Inc., Cary, NC) using the model of McDonald (1981) y = a + b (1 − e−c(t−lag)). Data were subjected to analysis as a factorial in a completely randomized design using the General Linear Model (GLM) procedure of SAS.
    Results
    Roasting increased dry matter (DM) content of both barley varieties (P<0.05). An increase in ADF and NDF content of roasted grain was due to decrease in water content of grain. Sahand variety showed higher degradability than Makoei (P<0.05). Dry matter degradability of both barley varieties decreased during 16 to 48 h of incubation due to roasting process (P<0.05); however, these varieties showed different kinetics of degradation during early period of incubation. Roasting increased DM degradability of the Sahand variety during initial 6 h of incubation; however, it showed different pattern in the Makoie variety. The rapid and slow degradable fractions (ie; a and b) decreased by roasting duration in both varieties (P<0.05). Also heat processing of barley grain resulted in a lower effective degradability of dry matter (P<0.01). Effective degradability of Sahand variety was higher than Makoie in all passage rates and all duration of heat processing (P<0.05). Fractional rate of degradability did not change by heat treatment. Makoei variety had higher water holding capacity (WHC), bulk density (BD), dry matter solubility (DS), and ash solubility (AS) than Sahand (P<0.05). Roasting increased WHC and decreased BD in both varieties (P<0.05) but had no effect on DS and AS. There were positive correlations between BD100 and Ether Extract (EE), NDF and ADF content of barley grain, which were 0.53, 0.40, and 0.35, respectively. Also, water holding capacity showed high positive correlation with NDF and ADF content (r =0.84 and r =0.71 respectively) and as expected conversely correlated with EE content (r = -0.61) of barley grain. Both of DMS and AS conversely correlated with EE content of barley grain (r = -0.24 and r = -0.49 respectively).
    Conclusions
    The results of the current study demonstrated that it is possible to decrease ruminal degradability of barley grain by using the right roasting treatment and choosing the proper variety. Makoei variety showed more decrease in fractional rate of digestion, which should be considered in the ration formulation
    Keywords: Bulk density, Grains, Heat processing, Water holding capacity
  • Z Nemati , A Karimi* Pages 65-80
    Introduction
    Growth performance of broiler chickens has been increased mainly due to the genetic progress, improvements of nutrition and controlled environment (Dastar et al. 2014). The increase in growth rate of modern broiler chickens has been associated with certain metabolic disorders such as ascites (Aftab and Khan 2005). These situations most commonly occur in broilers that had ad libitum feed consumption. It seems possible to reduce these problems by using feed restriction. Feed restriction is a technique of feeding where time, duration and amount of feed offering are limited, with expectation that the bird is able to reach the same body weight with ad libitum feeding (Yu and Robinson 1992). In general, feed restriction included of quantitative and qualitative restriction that is in quantitative to limiting the amount of offered daily feed to the birds; whereas, a qualitative restriction is related to nutrient dilution in the diet (Sedghi et al. 2018). Therefore, compensatory growth after feed restriction may have positive effects on feed efficiency and have more economical benefits (Zamani et al. 2013). This experiment was carried out to evaluate the effects of different levels of early and late feed restriction and consequently, compensatory gain, on performance and ascites index in broiler chickens.
    Material and methods
    Total number of 1000 one-day boiler chicks were used in a completely Randomized Design (CRD) and allocated to 8 experimental groups with 5 replicates per each group. Experimental groups included: 1) control group with no feed restriction (con), 2) 8 hours (8 h) daily feed restriction from 9 to 24 days of age (d), 3) 16 h feed restriction from d 9 to 21, 4) 24 h (every other day) feed restriction from d 9 to 18, and other groups: 5) 10 percent (10%) feed restriction, 6) 20% feed restriction, 7) 30% feed restriction, and 8) 40% feed restriction (from d 22 to 35). Feed consumption, body weight, FCR (feed conversion ratio) and EPF (European productivity factor) were measured weekly from 21 to 49 days of age. Blood sampling and sacrificing were carried out at day 49 of age and carcass segments and lactate dehydrogenase (LDH) and hematocrit of blood samples were evaluated. Ascites index as an indicator of cardiac function, was calculated by the cardiac right ventricular mass ratio to sum of the cardiac left ventricular and ventricular septum masses (Julian 1993). All data were analyzed based on a completely randomized design using proc GLM of SAS software and means were compared by Duncan multiple range test.
    Results and discussion
    Statistical analysis of 3 weeks of age indicated lower feed intake (FI) and body weight gain in 16 and 24 h feed restriction groups versus control group (p<0.05). There was no substantial difference between group 8 h feed restriction and control group; it seems that in spite of 8 hours feed restriction, birds compensate feed consumption in remained time and this result is in agreement with Mahmood et al. (2007) study. Also, lower feed consumption in these groups led to lower body weight at 3 weeks of age is consistent with Cornejo et al (2007) experiment. Feed intakes were lower in 20, 30 and 40% feed restriction groups at 4 weeks of age and lower in 20 and 40% groups at 5 week of age versus control group (P<0.05) that induced lower body weights than control group; but there was no significant difference in body weight at end of 6 and 7 weeks of age (P>0.05). The lowest total FI was observed in 24h group (P<0.05); whereas, 24 h group had the highest European performance factor (EPF). Though, there were no significant differences among experimental groups in total body weight, feed conversion rate (FCR) and EPF at 49 days of age (P>0.05). In consistent with Jalal and Zakaria (2012), relative liver weights were lower in groups with 24 h and 40% feed restriction than control group (P<0.05); but present study was contradictory regarding relative heart weight with no significant differences among experimental groups. Also, there were no significant differences in carcass traits, hematocrit, LDH and ascites index between experimental groups (P>0.05). Previous studies have expressed feed restriction in broiler chickens led to lower body weight and consequently lower ascites index (Dastar et al. 2014), while that is inconsistent with the present study.
    Conclusion
    it seems that 24 h daily (every other day) feed restriction from 9 to 18 days of age, resulted in lower feed intake, compensatory growth and proper EPF broiler chickens.
    Keywords: Ascites index, Compensatory growth, Feed restriction, Performance
  • S Ahmadi, S Alijani, MR Sheikhloo* Pages 81-96
    Introduction
    The unavoidable mating of related animals in closed populations leads to accumulation of inbreeding and decreased genetic diversity. The loss of diversity and an increase in homozygosity may result in decreased productions and fitness of inbred animals. It is apparent that different breeds as well as different traits vary in their response to inbreeding (Mackinnon 2003). It is important to account for the effects of inbreeding in populations undergoing selection to properly adjust the breeding program for the potential reduction in performance. The objectives of this study were to estimate the inbreeding trend and inbreeding depression on growth traits of Iranian Moghani sheep.
    Materials and methods
    Pedigree records on the research flock of the Iranian Moghani sheep kept at the Jafarabad Breeding Station from 1990 to 2016 were used for analysis. The pedigree completeness index (PCI) proposed by MacCluer et al. (1983) was used to describe the degree of completeness of pedigree. In addition, for each individual, the number of complete generations equivalent (CGE) was computed as the sum of (1/2)n, where n is the number of generations separating the individual to each known ancestor (Maignel et al. 1996). Inbreeding coefficient for all animals were estimated using the method of Meuwissen and Luo (1992). Average inbreeding coefficients per year were computed and annual increases in inbreeding were estimated by linear regression over time. Individual increase in inbreeding coefficients (ΔFi) was calculated according to the methodology described by González-Recio et al. (2007) and modified by Gutiérrez et al. (2009) as ∆Fi = 1− √1−Fit i −1 , where Fi is the inbreeding coefficient of individual i and ti is the number of known equivalent generations for this individual. The analyzed traits for estimating inbreeding depression were birth weight (BW), 3-month weight (3MW), 6-month weight (6MW), 9-month weight (9MW), and yearling weight (YW). For estimating the inbreeding depression, only animals with PCI > 0.6 were kept in all analyses. All animals were grouped into three classes: first class included non-inbred animals (F=0); second class included animals with 0<F≤0.10, and third class included animals with F>0.10. Then inbreeding included in the model as the categorical fixed effects. Also, in a separate analysis, inbreeding and individual increase in inbreeding were included in the model as a linear covariate.
    Results and discussion
    Proportion of animals with F=0, 0<F≤0.10 and F>0.10 in all population were 78%, 21%, and 1%, respectively. These proportions in animals with PCI>0.6 were 23%, 74% and 3%, respectively. Average inbreeding of all and inbred indivduals within the animals with PCI>0.6 were 1.00% and 1.32%, respectively. The rate of inbreeding is more important than estimated level of inbreeding in genetic management of the population (Falconer and Mackay 1996; Bijma 2000). The evolution of the mean inbreeding, pedigree completeness index (PCI), and complete generations equivalent (CGE) of animals across years of birth are given in Figure 1. Trend of inbreeding was more coincident with PCI than CGE. Such a discrepancies in the behavior of two index of pedigree completeness could be attributed to the differences in the computation methods. From the linear regressions estimated, the rate of inbreeding was 0.03% (P < 0.01) per year equal to 0.12% per generation in the studied period. This estimated rate of inbreeding was less than the critical levels (1% per generation) recommended by FAO (1998) and Bijma (2000). The estimated rate of inbreeding for Moghani sheep in this study was similar to those reported by Hossein-zadeh (2012) and Gholambabaeian et al. (2012) for this breed. Also it was close to values reported for Iranian LoriBakhtiari, Sangsari and Zandi sheep (Almasi et al. 2014; Rashedi Dehsahraei et al. 2013; Sheikhlou et al. 2017). Nevertheless, it was less than the estimates for the Iranian Karakul, Iran-Black and Baluchi sheep (Bahri et al. 2015; Mokhtari et al., 2014; Tahmoorespur and Sheikhlou 2011). This differences in inbreeding rate could be attributed to the differences in the pedigree completeness of animals and also to the low proportion of matings between relatives and better control of inbreeding in Moghani sheep. Table 3 shows the least square means for body weight traits in different inbreeding classes of animals. The mean BW and 3MW of animals in the second class was lower than non-inbred animals (P<0.05). However, means of the BW and 3MW of animals in third class were higher than the second class. In other words, some of the heavy animals were between the highly inbred animals. Similar to our results, Prod’Homme and Lauvergne (1993) reported increased prolificacy with increasing inbreeding. They concluded that the positive effects of selection and improved management on prolificacy were larger than the negative effect of inbreeding. However, it should be kept in mind that the low proportion of animals in the third class of inbreeding in this study may also have contributed to these results. According to the Table 3, means of the 6MW, 9MW and YW have decreased with increasing in inbreeding, but the differences between inbreeding classes were not significant. The regression coefficients of BW, 3MW, 6MW, 9MW and YW on inbreeding were 0.006, -0.023, -0.051, -0.017 and -0.119 and on individual increase in inbreeding were 0.022, -0.044, -0.185, -0.111 and -0.326, respectively and were not significant (P>0.05). Converting individual increase in inbreeding coefficients to the equivalent inbreeding for an animal with an average depth of pedigree resulted in inbreeding depression of 6, -13, -55, -33, and -96 gram in BW, 3MW, 6MW, 9MW and YW, respectively.
    Conclusion
    Considering the results obtained in this study, large proportion of animals in this flock with good pedigree completeness were inbred. Thus, implementation of methods to control inbreeding in this flock are suggested to achieve desired genetic gain with minimum loos of genetic diversity in the future. It seems that preweaning traits (BW and 3MW) is more affected by inbreeding rather than other growth traits in this breed. In this study the pattern of the changes in inbreeding depression due to using individual increase in inbreeding in the model were not the same across the different body weight traits.


    Keywords: Growth traits, Inbreeding depression, Individual increase in inbreeding, Moghani sheep
  • A Davariyan, S Khalaji, M Manafi , M Hedayati* Pages 97-111
    Introduction
    Nutrition is the most important and cost effective factor in poultry production. By reducing the nutritional cost, the production efficiency increases and the use of feed additives as growth promoters in poultry feeding is a way to achieve this goal. Medicinal plants have beneficial properties due to the biological active compounds such as terpenes, phenols, ketones, esters, and alkaloids that improve the animal performance and health (Abaza et al. 2008). From the category of medicinal herbs, Nettle (Urtica dioica) and Elaeangus (Elaeagnus angustifolia) can be introduced which both are from Rosales order (Mohammadi et al., 2017). Nettles may be used in veterinary medicine because of its high levels of nutrients such as amino acids, minerals, vitamins, active compounds such as tannin, folic acid, salicylic acid, carvacrol, and thymol (Fu et al., 2007). Elaeangus is also a shrub or tree of the Elaeagnaceac family of the genus Elaeagnus, called Elaeagnus angustifolia (Khakrizi & Salehi, 2012). Phytochemical experiments showed that the Elaeangus contains high amounts of flavonoids, cytosterols, carbohydrates, folic acid, and ascorbic acid. It also contains potassium, magnesium, sodium, iron, calcium, zinc, malic acid and calcium malate. It is rich source of fatty acids including linoleic, palmitoleic, and palmitic acids (Ramezani et al., 2001). In general, natural-food products, especially medicinal plants containing active biological compounds, can create a favorable outlook to be used in poultry nutrition. The use of medicinal plant resources as feed additive is growing rapidly due to their active aromatic compounds, which benefits the host animal (Mohiti Asl et al., 2011).
    Material and methods
    The experiment was designed and carried out using 128 commercial laying hens of W36 strain at 75 weeks of age with 4 experimental treatments, each group with 8 replicates and 4 birds per each replicate. A 14-day period was conducted to adapt the layers into the experimental diets. After this period, the main stage of the experiment consisted of 3 consecutive periods, each for 21 days, which totally with 11 weeks of the entire study period. During the experimental periods, the birds had free access to water and feed and the experimental diet was adjusted to maintain the requirements of the Hy-Line W36 (2014) breeding guidebook. The experimental groups consisted of: 1 (control): basal diet; 2: basal diet with 1% nettle powder; 3: basal diet and 1% Elaeangus fruit powder; 4: Basal diet plus 0.5% of nettle powder and 0.5% of Elaeangus fruit powder. The temperature and lighting program was also carried out according to the guide for breeding white Leghorn chicken (Hy-Line W36 strain). To evaluate the egg quality, three egg samples were taken and each egg sample was selected from each replicate. The sampling was done at the end of each periods. After sample collection, the weight of individual eggs were recorded using a digital top balance with 0.01 gram accuracy in the laboratory and later their individual specific gravity index were measured using a floating method in a salt water solution. The egg white quality was carried out by the Egg Multi Tester instrument (EMT-5200), (Leeson and Summers, 2005). To determine the thickness of the shell, Ultrasonic thickness Gauge (Echometer 1062 - Maks - USA) was used and to measure the shell resistance, the model-ll-MaksUSA device (Egg Shell Force Gauge) was used and the yolk color index was measured by the Rosche yolk color fan (Hosseini & Arshami, 2010). Shell weight were measured using a digital balance with an accuracy of 0.1 g (Leeson and Summers, 2005). The statistical analysis was done using SAS (2001) version 9.1.
    Results and discussion
    The highest amount of Haugh units belonged to the experimental group of Elaeangus fruit powder (1%) compared with control group and 0.5% nettle powder and 0.5% Elaeangus fruit powder group. The effect of experimental periods on the Haugh unit was significant and the highest number of Haugh units belonged to the second period, which had no significant difference with the first period, but showed a significant difference with the third period (P<0.05). The height of the egg white was statistically decreased in group 4 compared with control group (P<0.05). The effect of experimental periods on the height of egg white was significant and the highest amount was observed in the first and second periods compared with the third period (P<0.05). The experimental periods also had a significant (P<0.05) effect on the egg shell thickness, in which the highest amount was observed in the third period compared to the second period (P<0.05). Also, the interaction effect of the experimental periods and treatments on shell weight was also significant (P<0.05). Sayiedpiran et al. (2011) did not show any significant improvement using combination of extracts of thyme, mint, and Pennyroyal. Vakili (2011) indicated that, addition of essential oil of thyme and fennel into the diet of the laying hens, significantly improved the Haugh unit scores. Bird’s age and production stage are the effective factors on egg shell structure. The reason for improving the Haugh unit is attributed to the age of the bird, so the young birds have more Haugh unit scores. Also, Azghadi et al. (2010) reported no improvement in yolk color index using 0.1, 0.2, and 0.3% levels of thyme and cumin extracts. Vakili (2011) also stated in a study that adding 40 mg/kg of thyme extracts to the diet of laying hens showed no significant effects on egg shell quality parameters. Probably the reasons like the high age of chickens and the high temperature of the environment had a negative effect on the amount of calcium absorption to make the shell (Vakili, 2011).
    Conclusions
    Considering the results obtained from current experiment, it can be concluded that the use of Elaeangus fruit powder at 1% can be recommended to be used in layers diet.
    Keywords: Nettle, Elaeangus fruit, Egg quality, Laying hens
  • J Fayyazi, A Masoodi, R Abdolahi, A Rashedi* Pages 113-126
    Introduction
    Develop mentalists are often interested in understanding change processes; so, growth models are the most common analytical tools for examining such processes. Nonlinear growth curves are especially valuable to develop mentalists, because the defining characteristics of growth processes such as estimating initial levels, rates of changes during growth spurts, and asymptotic levels. A variety of growth models are described beginning with the linear growth model and moving to nonlinear models of varying complexity. A detailed discussion of nonlinear models is provided, highlighting the added insights into complex developmental processes associated with their use. Non-linear models can be an option to establish the mathematical behaviour of body development throughout the life of the Iranian sheep breed (Bahreini-Behzadi et al. 2010). These models require lower computational and faster convergence than other methods. Moreover, in genetic evaluation programs with large data sets, non-linear models are more advantageous. Non-linear models were analysed to describe both the biological and commercial growth curves of the Moghani sheep, one of the most important Iranian breeds. Growth models are mathematical functions which are applied for describing the growth pattern. Understanding, estimating, and capturing the defining characteristics of growth processes are key components of developmental research. The aim of this study was to estimate (co)variance components for growth curve parameters and investigate environmental effects on these parameters in Moghani sheep.
    Material and methods
    Data on body weight were collected by Jafarabad sheep-breeding station during 1995 to 2011. The number of records used to estimate (co) variance components of growth curve parameters for birth weight, weaning weight, 6-month weight, 9-month weight, and yearling weight were 7278, 5881, 5013, 2819 and 2883, respectively. Environmental factor such as, age of dam at birth, sex of lambs, type of birth, birth year, and birth season were studied on parameters of growth pattern. The procedure of SAS software was used for studying of fix effects. Based on body weight at different ages and using different initial values, each of the growth curve parameters was estimated using SAS software version 9.1 and NLIN procedure. Growth curve parameters (mature weight, growth rate, and mature rate) were estimated using 4 nonlinear regression models (brody, gompertz, logestic, and bertalanfy). After fitting different models and obtaining growth parameters, the best fit function was selected based on the amount of correction coefficient and corrected Akaeic index and the parameters of the growth pattern were calculated based on the selected function for each animal. The function has the lowest value of the Akaeic index and the highest amount of explanation coefficient, selected as the best function. Estimation of (co)variance components of growth curve parameters was conducted using Bayesian approach implemented in MTGSAM software. The number of Gibbs sampling rounds used was 200,000 rounds. Ten percent of these numbers (20,000 rounds) was burn-in. The convergence criterion for stopping repetitions in this analysis was also considered as 10 decimals (10-10). Sampling intervals of 400 and Gouss Seidel 10000 repetitions were considered. In order to find the best model incorporating the constant and random effects affecting each of the parameters of the growth pattern, the following models, with and without regard to maternal effects including maternal additive genetic effects and permanent maternal environmental effects in the model (Meyer’s models) were tested.
    Results and discussion
    The Von Bertalonfy model presented the highest R2 and the lowest AIC compared with the other models and selected as the superior model. Environmental factors such as birth year, sex, and age of mother had significant effects on the mature weight (A) and growth rate (B). Fix effects of birth year and sex had significant effect on the mature rate (K), (P<0.01). Among the six linear models, according to minimum residual variance for mature weight model 4, for growth rate model 6, and for rate of maturity model 5 were selected. Using the most appropriate models in Bayesian approach, the direct heritability for curve parameters was 0.29±0.003, 0.35±0.004 and 0.21±0.004, respectively. The genetic correlation between all the growth curve parameters was positive and small and its value between A and B was 0.007, between both parameters A and k 0.001 and between B and k 0.009. The results obtained in this study contradicted the results of some researchers in this regard (Mollaei et al.2013). The difference in the estimates of different researches depends on the type of model used for analysis, the breed of sheep, and the structure of available information to estimate the parameters, the differences in the management of different herds and the application of different breeding programs (Bathaei and Leroy, 1998).
    Conclusion
    According to the results, the effect of environmental factors on the parameters of the growth pattern is important and should be investigated in the analysis of these parameters.
    Keywords: Bayesian approach, Growth pattern, Moghani sheep, Nonlinear-functions
  • F Shahverdi, M Vatankhah, AA Shadparvar* Pages 127-138
    Introduction
    One of the breeding programs for sheep is the nucleus breeding scheme (Kosgey and Okeyo 2007). The nucleus breeding system, including open or close nucleus, is a good start for genetic improvement in many populations. Unlike the close nucleus schemes, there is a reciprocal gene flow in open nucleus schemes, where the best animals from base layer could be transferred to the nucleus layer (Kosgey et al. 2006). In the original nucleus breeding scheme, a constant genetic variation was assumed for the trait of interest across different generations (Hopkins and James 1978). However, it is well realized that the additive genetic variance is decreased after several generations of intense selection. Thus, the actual genetic gain is likely less than the expected genetic gain. In other words, the outcomes of these breeding schemes are likely affected by the intensity of selection as well as the relative size of the nucleus population to the size of whole population. The aim of current study was to investigate the effect of relative nucleus size at three levels of 5, 10 and 15 percent and the effect of selection intensity in males and females at three levels of high (i.e. selection proportion in male and female candidates were 1 and 20 percent, respectively), moderate (i.e. selection proportion in male and female candidates were 5 and 50 percent, respectively) and weak (i.e. selection proportion in male and female candidates were 10 and 80 percent, respectively) on the amount of biasness of predicted genetic gain due to ignoring the effect of selection on genetic variance.
    Material and methods
    An open nucleus breeding scheme was deterministically simulated using data from Lori Bakhtiari sheep breed, consisting a nucleus herd of 1005 ewes and a base herd of 4019 ewes (Vatankhah 2005). Birth weight was the breeding goal trait and selection was carried out using one individual performance record. The generation was assumed to be overlapped and three and six age groups were considered for males and females, respectively. The age of parents at first lambing was 2 years and 0.94 yearling lamb was produced per ewe. One ram was mated to 33 ewes. The additive genetic variance for breeding goal trait was 0.11 and its heritability was set to 0.30.
    Results and discussion
    For a given size of the nucleus and a constant rate of transferring ewes from base population to nucleus (x), there was an optimum rate of migration of nucleus rams into the base population (w), that maximized the expected genetic gain and minimized the genetic lag between nucleus and base populations, with or without accounting for the effect of selection on the genetic variance. By increasing the relative size of the nucleus, from 5 to 15 percent of whole population, the biasness of the predicted genetic gain was increased from 11.84 to 16.67 percent. At a given rate of x, the bias of genetic gain prediction which originated from ignoring the effect of selection, varied nonlinearly as the rate of w increased and had a minimum value at the optimal value of w. At a particular rate of w, increasing the rate of x, was associated with higher rate of bias. The rate of bias increased from 12.2 to 16.54 percent, as the intensity of selection increased. The reason could be the markedly reduction in the genetic variance of considered trait due to selection at high selection intensities. In open nucleus schemes, the amount of bias changed from 14.18 to 17.72, as a consequence of increasing the intensity of selection. Across all levels of selection intensity in open nucleus programs, the lowest bias was observed at the rate of 0.75 for w. Evaluation of joint effect of relative nucleus size and intensity of selection, showed that at high selection intensity and relative nucleus sizes higher than 10 percent, the amount of bias was not likely to be influenced by nucleus size.
    Conclusion
    Ignoring the effect of selection on genetic variance could result in a biased prediction of genetic gain in the nucleus breeding schemes. However, the optimal ram transfer rate from nucleus to base population was independent from the effect of selection intensity. The lowest bias was observed for the scheme with optimum transfer rate. Results of the current study revealed that at weak selection intensity, the effect of selection could be ignored and the breeding program could be optimized for ram transfer rate from nucleus to the base populations. However, at high selection intensities, the ignorance of this effect might result in wrong conclusions.
  • Sh Kargar, F Fathi* Pages 139-152
    Introduction
    An adequate supply of good-quality food is essential for human health and well-being. Milk and meat products derived from ruminants represent important sources of nutrients in human diets, providing energy, high quality protein, and essential minerals and vitamins. Nutritional quality is increasingly an important consideration in food choices, because of the growing consumer awareness of the link between diet and health. Many foods contain micro-components (i.e. conjugated linoleic acid, omega-3 polyunsaturated fatty acids, and odd- and branched chain fatty acids) that have beneficial effects beyond those associated with their traditional nutrient content, and these are often referred as functional food components (Bauman et al., 2006). The epidemic of obesity in most highly developed countries has led to an understandable public health emphasis on low fat, low energy diets, and has provided a major stimulus for development of low fat products and fat substitutes as a means of reducing the prevalence of coronary heart disease. However, recent research suggests that there is a need to consider the quality as well as the quantity of fat in human diets (Williams, 2000). According to the recent reports, coronary heart disease is one of the most important factors affecting human mortality in the world which is associated with human feed regime (Bauman et al., 2006). This type of disease is a serious menace for human societies and scientific societies with different disciplines should have a collaboration to reduce the probability of occurrence of such disease. Accordingly, as a practical approach, production and supply of enough amounts of functional foods (dairy products) would be able to play a fundamental role in human health and well-being. Conjugated linoleic acid and its precursor is existed in ruminant animal driven products like milk and meat which have anticarcinogenic, anti-platelets accumulation, anti-obesity, anti-oxidant, and immune system modulation properties (Bessa et al., 2000; Williams, 2000). Furthermore, the beneficial effects of omega-3 polyunsaturated fatty acids intake (especially eicosapentaenoic acid and docosahexaenoic acid) on heart health, and avoiding diabetes (type 2), high blood pressure, cancer, and disorders of the nervous system have been reported (Williams, 2000). Unfortunately, the current human diet is very high in omega-6 fatty acids (the ratio of omega-6 to omega-3 fatty acids is 20–30:1 instead of the traditional range of 1–2:1) because of the indiscriminate recommendation to substitute omega-6 fatty acids for saturated fats to lower serum cholesterol concentrations (Simopoulos, 1999). Intake of omega-3 fatty acids is much lower today because of the decrease in fish consumption and the industrial production of animal feeds rich in grains containing omega-6 fatty acids, leading to production of milk and meat rich in omega-6 and poor in omega-3 fatty acids. Hence, it is necessary to find possible and potential approaches to increase contents of conjugated linoleic acid, omega-3 fatty acids, and other bio-active components in a safe, cheap, and easily available dairy products like milk. Despite this, consumer willingness to pay is another key factor that will affect industry interest (due to imposing some additional costs) to produce and supply of milk with functional food properties. Therefore, the main goal of this study was to investigate consumer willingness to pay (WTP) for a milk with functional food properties in Shiraz, Fars province and also, study of factors influencing this willingness.
    Material and methods
    The data applied in this study were collected through a Contingent Valuation (CV) survey in 2017 in Shiraz, Fars province. in this study, 279 questionnaires were evaluated using the Cochran method and pretest information. The questionnaire was divided into four sections. In the first section information about milk with functional food properties was given. The second section consisted of questions regarding personal information about the respondent and respondent’s socio economic status such as, age, gender, income and education. The next section contained attitudinal questions to extract information about respondent’s attitude about this milk, as their attitude was evaluated by offering five options: very high, high, medium, low, and very low; and the fourth section sought information about respondent’s willingness to pay for this milk. In this study, variables such as age, gender, family number, education, income, marital status, employment and monthly frequency of use were used to estimate Tobit and line regression models (two step Heckman model). Except of age, family number and monthly frequency of use, all explanatory variables were binary (zero or one) and integers. After extracting the necessary data from 279 questionnaires, socio-economic characteristics are reported in Table 1,2, 3 and 4. Before proceeding to the results, general information should be obtained from the sample.
    Results and discussion
    The purpose of the estimated model was to measure the impact of the most relevant explanatory factors on the consumer WTP. The result of estimation reported in tables 4. Respondents indicate that milk health, milk quality, and prices are the most important factors to increase milk demand consumption. One hundred forty-three respondents think that the milk production stage is an important factor in controlling healthy milk. Based on these results, one of the most important factors that influence the WTP is the monthly frequency of milk use (1.5). Marginal effects and elasticity of explanatory variables on WTP probabilities were shown in Table 4. The marginal effect of family income indicated that 1 unit increasing on income, increased 5.6 ×10-8 unit probability of WTP. Education variables is significant at 5% level and has positive relationship with the probability on WTP. Result indicate that education change one to upper level, increased 0.042unit probability of WTP .one unit on monthly frequency of milk consumption Increased 0.052 unit probability of WTP (marginal effects) and 1% increased on monthly frequency of milk consumption 0.212 percentage probability of WTP increased (elasticity). Generally, women are more concerned with health issues than men, and therefore have a relatively higher WTP for this milk. Consumers with a higher level of education and the higher average household income will be willing to pay a greater price for milk with functional food properties. Young people compared to older have a relatively higher WTP for this milk, because disease prevention is most important for young people. This research revealed that educational level of household head had positive effect on WTP. The results of models reveal that all the factors hypothesized to positively influence consumers WTP, except for gender, age and family number factor.
    Conclusion
    Consumers were willing to pay an additional 2784 Rials for food safety, which will account 19% increased price compared to the normal milk.
    Keywords: Milk with functional food properties, Tobit, Two -steps Heckman, Willingness to pay
  • Gh Dashti, R Pahlavani, F Sani, M Ghahramanzadeh* Pages 153-168
    Introduction
    The small ruminant husbandry is one of the most important and the most experienced activities in the agriculture sector that this has an important role in the establishment of public health and provision of food security, making employment and also lateral industrial affluence. There are two rural and pastoral systems for small ruminant husbandry in our country. During the last years, the government has been done many efforts for elevating and optimizing the Total Factor Productivity (TFP) of this economic activity. In this context, the purpose of this study was to investigate the effectiveness of the government support policies on total factor productivity in two rural and pastoral systems of the small ruminant husbandry during 1997-2013 in four selected provinces including Lorestan, Kermanshah, Hamedan, and Ilam.
    Material and methods
    In order to estimate the amount of government support, the Producer Support Estimate (PSE) was used based on the indexes of the OECD and so, the TFP was calculated by Divijia Index. Then, the Im–Pessaran–Shin (IPS) unit root test is used to test the stationary of variables in panel data sense and the Pederonic's panel data cointegration test was applied to check existence of the cointegration relationship. The long run relationship was estimated between PES and TFP in both systems by Generalized Method of Movement (GMM) producer in both pastoral systems of small ruminant husbandry in selected provinces of Iran. Also, the Sargan test was carried out. The required data were gathered from Agricultural Bank, Agricultural Organizations, Office of Tribal Affairs, Central Bank of Iran and OECD over 1997-2013.
    Results and discussion
    Findings of this study showed that Producer Support Estimate (PSE) in the rural system is more than the pastoral system, because in some way receives more protection of government based on the indexes of the OECD. Ranking of provinces from point of view of government protection in rural system based on the index of PSE is Kermanshah, Hamadan, Lorestan and Ilam and in pastoral system are Lorestan, Kermanshah, Hamadan and Ilam. Also the amounts of the growth rate of TFP based on Divijia index are calculated in both systems. From the point of view of the average of TFP as compared with the base year, 2004 ranking of the selected provinces in case study in rural study include Ilam (100.73), Lorestan (100.4), Kermanshah (100.3) and Hamadan (99.84) and in pastoral system include Ilam (100.89), Kermanshah (100.59), Lorestan (100.54) and Hamadan (10084). Im-Pessaran-Shin (IPS) method was used for determining the stationary of variable in panel data that showed total variable were I (1). Pedronic test was applied for determining of cointegration and showed long-run relationship among variables. Generalized Method of Movements (GMM) was applied for estimating the long-run relationship among endogenous variable (Total Factor Productivity) and exogenous variable (PSE, amount of labor and capital). Findings indicated that amounts of impact partial elastic of the Total Factor Productivity from the producer supporter estimates (PSE) labor force and capitals in rural system were 0.1691, 0.1998, and 0.9269 and in the pastoral system were 0.6190, 0.16 and 1.041, respectively. Thus, the coefficient of effectiveness of government support policies on Total Factor Productivity (TFP) in pastoral system is more than rural system. The reason of pastoral system superiority, from the point of view of the government support policies can conceive in this system characteristic such as less fixed and variable cost, more using of the growth season, concentration producing management, expansion of the market, and efficiency of product's capability in various markets and learning more experiences skill by producers for working skillfully.
    Conclusion
    The results of the study indicated that the factors of productivity and its growth in the rural and pastoral system are low. Also the both systems have empty capacity of production. Therefore, it is suggested that the government made the suitable policies to promote productivity in line with relative advantages and existence capacities. Based on the results, it is suggested that to form a new system by the name of summer migration by integration of these two systems. It is evident that the result of this study can help government support politics’ aim to increasing Total Factor Productivity in this field of activity and at last the increase of international wealth and sources. Since the effect of government support on total productivity factors in pastoral system is less, it is suggested that the amount, composition and timing of government assistance should be improved.
    Keywords: Government Support Policies, GMM, Panel Data, Small Ruminant, Total Factor Productivity
  • Sh Basiri, V Taheri, V Attari* Pages 169-179
    Introduction
    In recent years, the interest has been increasing in the use of medical plant in animal. Use of herbs was due to increasing in milk property. So, many researchers have been studying in this subject. Results of these researches indicated higher milk production in which supply of these drugs and their ingredients called milk enhancers or galactogogues. The increase in milk due to the use of these drugs varies depending on the type of livestock and the amount of production. Lactation is affected by nutritional and non-nutritional factors (related to endocrine, health, weather, and management) that play a role in the synthesis and secretion of milk. Chemical or herbal modifiers stimulate, maintain and increase milk production (Mortel and Mehta 2013). This study was conducted to assay the effect of galactogogues plants combination (GPC) included fennel, black seed, and black caraway powder in diet on milk production, prolactin and growth hormone levels in lactating dairy cows.
    Material and methods
    A completely randomized design was used with 12 Holstein cows having 620±15 kg live weight, 30±10 days in milk, and 33±10 kg/day average milk production in a farm of Ardabil city, Iran. Cows were assigned to one of the two treatment group: 1- control (n=6) they fed basal diet based on NRC (2001) recommendation for dairy cow requirements and (2-GPC) group (n=6) fed basal diet with galactogogues plants combination powder 0.03% of body weight which consist of fennel, black seed and black caraway mixed with concentrate. The experiment continued 8 weeks after one week of adaptation period. Milk production was recorded and milk composition was measured. At the end of experiment, blood samples were taken from jugular vein of all animals and then, sent to the lab to assay prolactin and growth hormone levels.
    Results and discussion
    the results showed that milk production increased in animals fed herbal treatment (P<0.0001), this result is consistent with Kholif and Khorshed (2006); Abo El-Nor et al. (2007). Relative improvement in milk production may be due to its effect on livestock health (because incidence of disease cause waste of nutrients for fighting pathogens) and also may affect on acetate and succinate production of ruminal microflora, which lead to improvement in nutritional efficiency and milk production (Kholif and Khorshed 2006; Abo El-Nor et al. 2007). Milk composition percentage showed no significant change in this study, while daily produced milk composition increased significantly associated with milk production (P<0.05). These findings are in accordance with other studies (Nurdin et al. 2011; Afshar Hamidi et al. 2013). Prolactin and growth hormone levels tended to increase, but showed no significant change. A significant overnight release of prolactin hormone observed in lactating goats associated with morning and evening milking (Hart, 1974). Research on mice has also confirmed that this hormone increases by sucking milk (Sar and Meites, 1969). On the other hand, it has been reported that galactogogues compounds stimulate activity and number of alveoli, so it resulted in increasing of milk secretion (Ravikumaretal., 2008). In the study of Salahshoor et al. (2012), intraperitoneal injection of alcoholic extract of nettle in doses of 25, 50, and 100 mg/kg for 21 days in female rats, significantly increased the number of alveoli. However, the increase in the amount of prolactin hormone and alveolar diameter were not significant. They concluded that the effect of nettle on the increase of milk could be due to the supply of essential nutrients that the mother received from the plant and does not related to the effect of produced prolactin hormone. Turkyilmaz et al. (2011) suggested that the effect of herbal galactogogues can be attributed to their phytoestrogenic activity. These molecules may be similar to 17-estradiol which is an endogenous estrogen and stimulates the proliferation of the epithelial cells of the breast. Therefore, based on the results of previous studies, this ineffectiveness can be considered in the amount of compound used, the type and condition of livestock and the method of application such as extract or leaves, or in the oral or injection form, duration of using and may be because of other factors. So, more studies are needed to find more accurate results.
    Conclusion
    Based on the present results, it was concluded that using galactogogues plants combination improved milk production in cows, while composition of milk yield showed no significant difference. Dosage of plant powder in this study did not affect growth hormone and prolactin.
    Keywords: Galactogogues plants, Growth hormone, Holstein cows, Milk production, Prolactin
  • M Alikhani, A Riasi, GR Ghorbani , A Shahmoradi* Pages 181-193
    Introduction
    Transition period (3 weeks before to 3 weeks after calving) is a critical period for cows' health and production (Grummer 1995). During the late gestation, nutritional demand of fetus increases considerably, while feed intake reduces more than 30 percent during the last 3 weeks of gestation (Sadri et al. 2012). Nutritional strategies are important for preventing the decrease in DMI during close up period. On the other hand, rapid increase of postpartum DMI could reduce the severity of negative energy balance, and therefore, improve milk production and health (Poláková et al. 2010). Grummer (1995) reported a positive correlation between DMI at d 1 prepartum and d 21 postpartum. Several nutritional approaches for the close-up diet have been proposed to stimulate prepartum DMI and minimize lipid mobilization: 1) use of bulky forage NDF sources into the diet to increase ruminal fill, 2) increase in dietary fat or NFC content of the diet to increase energy intake, 3) use of appetitive feeds for increasing in DMI and preventing ruminal acidosis and 4) use of feed additives that serve as gluconeogenic precursors to increase energy supply (Dann, et al. 2007). These approaches have yielded variable results in research and production settings. Diets with high levels of NFC are more common, but these diets may lead to acidosis and feed intake depression (Wang et al. 2013). In addition, readily fermentable carbohydrates (i.e. barley grain), increase ruminal propionate production and propionate can lead to reduction e in feed intake (Allen. 2009). Beet pulp is a unique feed ingredient containing 40% NDF with highly soluble fiber content (especially pectic substances) (Dann et al. 2007). There are different results for replacing grains with dried beet pulp in dairy cows nutrition. Clark and Armentano (1997) reported an increase in DMI of cows after replacing of shelled corn with dried beet pulp. However, some researchers demonstrated that dried beet pulp had no effect on cows' milk yield (Mahjubi et al. 2009; Clark and Armentano 1997). Although, Mahjubi et al. (2009) with replacing 50% of barley grain with beet pulp reported an increase in milk fat percentage. This study was designed to investigate the effect of different form of non-fibrous carbohydrates (lipogenic vs. glucogenic) diets on feed intake, performance, and ruminal pH in transition dairy cows.
    Material and methods
    All procedures were conducted under protocols approved by the Isfahan University of Technology (IUT), Laboratory Animal Care Advisory Committee. The experiment was conducted in Lavark at the Farm Animal Research and Teaching Unit of IUT. Twenty-four multiparous (1-3 parity) Holstein cows were kept in 9 m2 individual pens from 4 weeks before to 4 weeks after parturition. The animals have free access to feed and fresh water. In this study, pelleted beet pulp ground by a 2 mm screen was used as a partially replacement for ground barley grain. Twenty-four multiparous Holstein cows were fed a total mixed ration containing 100% barley as a grain source of concentrate and no beet pulp (BP0, Glucogenic Diet, GD) and in 2 experimental rations 25 (BP25, Low Lipogenic Diet, LLD) and 50% (BP50, High Lipogenic Diet, HLD) of barley grain in the glucogenic diet was replaced by beet pulp, from d 21 before anticipated calving to d 24 after calving. The experimental diets were formulated according to Cornell Net Carbohydrate and Protein System (CNCPS, v. 6.1, Cornell University, Ithaca, NY) for pre and postpartum periods. Data were analyzed as a block randomized design (parity as blocks). Daily DMI was determined by subtracting orts from offered TMR and were recorded for individual cows. After parturition, cows were milked three times daily in a milking parlour, and milk production was recorded at each milking time. Milk samples were collected weekly from three consecutive milking, and preserved using potassium dichromate. Milk samples were analyzed for fat, protein, lactose and total solid by an automated near infra-red spectroscopy analyzer (Milk-O-Scan, 134 BN, Foss Electric, HillerØd, Denmark). Body weights were measured weekly pre and postpartum (from d -28 to d +25) and the changes in BW were calculated. Postpartum net energy balance (NEB) for each cow was calculated based on NRC (2001).
    Results and discussion
    Results showed that during the prepartum period, DMI (kg/d), DMI (%BW), and energy intake (Mcal/d) were increased by substitution of barley grain with dried beet pulp (P<0.01); however, the change in DMI as a percentage of BW from d 19 to d 1 before parturition was not affected by treatments. During postpartum, DMI (kg/d), DMI (%BW), and energy intake (Mcal/d) increased as a quadratic effect (P<0.01) with the increasing levels of beet pulp replacement. Body weights, back fat thickness and postpartum calculated net energy balance were not affected by the treatments. During postpartum, milk yield was the lowest by using HLD (P<0.01). However, 4% FCM and ECM and total solid of milk were not affected by the treatments. HLD significantly increased milk fat percentage (P<0.05) and decreased milk protein percentage (P<0.07) in comparison with the GD and LLD. During postpartum, ruminal pH was the lowest in GD (P<0.05).
    Conclusion
    Results suggest that using of LLD in periparturient diets increased DMI, energy intake, milk yield and improved rumen health.
    Keywords: transition period, beet pulp, barley grain, glucogenic, lipogenic