مجله علوم دامی ایران
سال چهل و چهارم شماره 2 (تابستان 1392)

A number of 5558 lambing records of 2245 Mehraban ewes، collected during years 1995 to 2010 were utilized to estimate the variance components and heritability for the number of lambs per lambing، making use of B-Spline random regression models. The fixed factors affecting the studied trait were identified using general linear model analysis as well as SAS software، where flock-year-season and the age of ewe at lambing (month) had significant effects. Variance components were estimated as based on linear، quadratic and linear-quadratic B-Spline random regression models with 4 to 6 knots، using WOMBATsoftware. The models were compared using AIC and BIC indices، out of which model QLL4 (quadratic for fixed regression and linear for additive genetic، as well as permanent environmental effects with 4 knots) was found out as more suitable than the others. According to this model، estimates of additive genetic، permanent environmental، and phenotypic variances of a number of lambs per lambing stood in the ranges of 0. 01 to 1. 24، 0 to 4. 09 and 0. 34 to 5. 98، respectively. Moreover، heritability estimate for the studied trait was in the ranges of 0. 02 to 0. 28. The heritability estimates for the number of lambs per lambing at 60 to 72 months of age were higher than those for the other ages.

Calpastatin has been introduced as an effective candidate gene as regards growth efficiency and meat quality traits. Throughout the present study، blood sampling as well as carcass trait measurements were performed on 74 Lori-Bakhtiari sheep and on 40 Zel-Atabay cross-breds from industrial slaughterhouses of Shahrekord and Gorgan cities، respectively. Following DNA extaction، Polymerase Chain Reactions were performed for amplification of a 254 bp fragment containing the entire exon 6 of calpastatin gene. SSCP method along with silver staining were employed for genotyping of PCR products. Fourteen genotypic patterns namely: AA، BB، AB، AC، AD، BE، AF، AG، AH، AI، JJ، AJ، BK، and AL were observed with frequencies of 0. 035، 0. 123، 0. 105، 0. 114، 0. 009، 0. 053. 0. 316، 0. 027، 0. 017، 0. 017، 0. 009، 0. 105، 0. 017، and 0. 053، respectively for the two breeds. The calpastatin gene significantly affected live weight before slaughter، fat-tail weight (p<0. 001)، percentage of the fat-tail to carcass weights (p<0. 01) as well as fat bearing carcass weight (p<0. 05). Genotype AB was found as the superior genotype for all the traits. The favorable genotype for growth traits was AJ، whereas BE being the favorable one for weight and for percentage of fat-tail (animals with BE genotype bore a smaller fat-tail) but this genotype along with genotype BB were unfavorable as regards growth traits.

Identification of effective major genes releted with energy balance، milk production، fertility، immunity، as well as feed consumption constitutes some of the most important and strategic objectives in animal breeding and genetics researches. Among the major genes، leptin is one of the largely effective ones the polymorphism of which is closely related with important economic traits in livestock. Throughout this study، 100 blood samples were randomly collected from Naeini sheep breed. DNA was extracted using modified salting out method and Polymerase Chain Reaction employed for amplification of a fragment of 275 bp length from exon 3 of leptin gene. The two methods of PCR-SSCP and DNA sequencing were employed for identification of different genotypes. Results showed a single nucleotide mutation of A to C in the nucleotide position of 49 (in the amplified fragment) indicating a type of silent mutation. The frequency of each A and C alleles and of the two AA and AC genotypes were determined at 0. 73 and 0. 27، respectively. In the course of this research work، the observed effect on growth and wool production traits was also evaluated. The birth weight in sheep with AC genotype was higher than that in animals with BB genotype (P< 0. 01)، but there was no other significant effect of the observed genotypes on the other studied traits. It can be concluded that in the case of repeated results obtained from further research in the future studies، (of higher sample sizes) it may be possible to use either this marker site or other sites (relevant to leptin gene) in selection programs as based on molecular DNA markers.

The Toll-like Receptor 4 (TLR4) is an innate immune protein on cell surfaces that identifies Lipopolysaccharide (LPS) of gram-negative bacteria. Genetic markers associated with innate responses during mastitis could help in selection of cattle to improve disease resistance. The objective of this study was to determine the association between TLR4 gene and clinical mastitis، using selective genotyping method. A total of 270 cows of two extreme groups namely: top clinical mastitis resistant vs. top susceptible ones were selected. For genotyping، the 2 methods of: PCR-RFLP and PCR-SSCP were made use of. Identified polymorphisms induced A-G in exon 2، and C-T in exon 3. Following sequencing، polymorphism effects on clinical mastitis were analyzed using logistic regression. The results indicated that TLR4 gene was significantly associated with clinical mastitis resistance.

Pedigree information of Iranian Holstein dairy cattle، collected via Animal Breeding Centre of Iran from 1971 to 2007، were utilized to describe the reasons for the increasing inbreed coefficient. Inbreeding coefficient (F) and Pedigree Completeness (PCI) of all the available cattle were found out using a pedigree structure of 883713 animals. The herds with PCI of above 0. 85 were picked out and divided into two groups، one group (G1) with high F (and PCI=0. 97) and the other (G2) with low F (and PCI=0. 95). For each group، a reference population (animals born within years 2002 to 2007) was defined and the pedigree traced back. The number of individuals picked out from the pedigree were 35638 and 41850، for G1 and G2 respectively. The probability of gene origin (effective number of founders، founder genome equivalent and non-founders) were estimated for both groups. The number of founders، effective number of founders، founder genome equivalent، non-founders، and the number of founders، contributing to 50% of the gene pool of reference population were recorded as 5226، 296. 84، 9. 31، 9. 61، and 134 in G1 and while 7562، 331. 46، 16. 78، 17. 67، and 153 in G2، respectively. The results finally indicated that the higher inbreeding coefficient in Iranian Holstein may be attributed to a small number of effective founders.

The objective of the present study was to determine the effects of different levels of L-arginine in the diet on the growth performance، carcass traits، and blood parameters of female Ross broiler chickens within their starter period. A number of، 192 day old female Ross broiler chickens were fed with 4 dietary treatments in a completely randomized design، each dietary treatment had 4 replication. Dietary treatments included 100، 153، 168 and 183% of digestible arginine، as based on the Ross catalogue recommendation. The birds، were fed from day 1 to 10. On the 10th day of experiment، three chickens per replication were randomly selected، blood samples were collected from each، and then the birds were slaughtered to measure carcass traits and determine blood parameters. The results revealed that dietary arginine treatments significantly (P<0. 05) affected the increase in 10-day body weight، daily weight gain، feed efficiency، carcass weight، carcass efficiency، weight and thickness of breast muscle، thigh weight، heart weight، weight plus length of duodenum، jejunum، and ileum; while decreasing (P<0. 05) carcass abdominal fat weight. Arginine supplementation also increased (P<0. 05) plasma concentrations of triiodothyronine (T3)، thyroxin (T4while decreasing (P<0. 05) plasma concentrations of cholesterol، triglyceride، and urea. According to the results of the study، a consumption level of 168% digestible arginine، as based upon Ross catalogue recommendations، rendered the most desirable results on growth improvement and carcass traits، while the diet containing 183% digestible arginine، also based upon Ross catalogue recommendations، led to the greatest fat carcass reduction.

The objective of the current study was to investigate the effects of sex and carcass weight on the fatty acid composition in Longissimus dorsi in Zel lambs. Thirty pasture reared lambs (15 males and 15 females) were randomly selected from local flocks. Following slaughtering، the carcasses were assorted into two groups، according to their weights (>15kg and <15kg). Back fat thickness as well as intramuscular fat weighed more in female lambs and as well in lambs of greater than 15 kg carcass weight (p<0. 05). Females and heavier lambs (>15kg carcass weight) bore higher a* (redness) than males and than lambs of less weight (p<0. 05 and p<0. 01، respectively). However، males showed higher b* (yellowness) than female lambs (p<0. 05). Cooking loss and shear force in females were recorded as less than those for male lambs (p<0. 05). SFA/PUFA ratio was observed to be greater in female lambs and in lambs of more than 15 kg carcass weights (p<0. 05). The ratio of n-3: n-6 PUFA in less weighted lambs (<15 kg carcass weight) was lower than that in heavier lambs. Meat from males was of a lower atherogenic Index (AI)، as compared with that from female lambs (p<0. 05). In total، meats from males and from lambs of lower than 15kg carcass weight were observed to be of more desirable nutritional characteristics and color quality.

Lysozyme is one of the bioactive components of eggs with well known antibacterial potential، widely used in food industry، medicine and pharmaceutics. In this study، the possibility of quail’s egg lysozyme concentration and activity (modified via amino acids dietary supplementation) was investigated. In accordance with lysozyme amino acids profile، four amino acids of: asparagine، arginine، glycine، and methionine were added to layer quails’ feed. For supplementation of amino acids، provision of the same level of protein content in all the groups was considered، so that amino acids were supplemented in such a way as to add 0. 235% protein to the basal diet. A total of 72 Japanese quails were employed in a completely randomized design experiment of six experimental groups، three replicates and four birds in each of the 18 cages. Amino acids supplementation was proved to have significant increasing effect on egg number and on total egg،s mass production (P<0. 05). Feed conversion ratio did not significantly differ among the experimental groups، but the most desirable ratio was observed in the control group. Egg shell weight، percentage of albumen، percentage of yolk، albumen height، Haugh unit and yolk height showed significant differences among the experimental groups (P<0. 05). Supplementation of amino acids to the diet improved these parameters of eggs. Lysozyme activity was assessed via lysoplate and turbidity methods. Supplementation of arginine and asparagine alone and in their combinations increased the lysozyme activity as evaluated by lysoplate (P<0. 05) and by turbidity (P<0. 05) methods. Lysozyme concentration was also influenced by a supplementation of the mentioned amino acids (P<0. 05).

This experiment was conducted to determine the AME، AMEn، TME and TMEn of beet pulp fed to male ostriches at their 90 d of age. Different levels of beet pulp (0، 15، 30 and 40%) were fed through replacements in the basal diet. For a determination of AME and AMEn using marker method، beet pulp was replaced in the basal diet at 40%. A number of 16 vs. 8 ostrich chicks were employed in each of the total collection vs. marker methods، respectively. A completely randomized design of 4 replicates was adopted. AME and AMEn were determined via chromic oxide marker and via total excreta collection methods. The AME and AMEn for beet pulp were recorded as 3199±238، 2902±95، 3125±214 and 2798±86 kcal/kg (at 40 % of replacement) as assessed through chromic oxide marker and total excrete collection، methods respectively. Assessment of TME and TMEn of beet pulp as based upon different levels of feedstuff were recorded 3215 and 3134 kcal/kg respectively. The results finally indicated that use of the ME data assessed via adult leghorn cockerel (in formulating the starter diet for ostrich) is not applicable، and values of ME in ration formulation regarding ostrich are to be determined

This research was conducted to assess the effect of substituting corn for barley grain in diet on performance and reproductive characteristics of early lactating، Holstein dairy cattle. A number of fifteen cows in their second lactation (26±11 DIM) with 36. 7±5. 6 kg milk/d were investigated for 75 day (15 day for adaptation and 60 day for sampling) in a completely randomized design. The iso-energetic and iso-nitrogenous diets contained different levels (80، 160 or 240 g/kg DM) of corn substituted for barley grain. Feed was offered ad libitum as total mixed ration. In the experimental period، daily Dry Matter Intake (DMI)، milk yield، body weight blood chemistry parameters، as well as reproductive characteristics were recorded. The DMI، milk yield، milk fat and protein percentage، plasma glucose and insulin concentrations، Services Per Conception (SPC) and Open Days (OD) for the cows fed the diet containing 80 g of corn/kg DM، respectively، were 24. 76، 42. 07 kg/d، 3. 26 and 2. 98%، 60. 1 mg/dL، 0. 409 µg/L، 1. 6 and 95. 8 d. Daily DMI، milk yield and feed efficiency were recorded as similar among treatments. Increasing the level of corn in the diet did not affect milk fat، protein and lactose، although the percentages of protein and fat were، numerically slightly increased. With increase in the level of corn in the diet، plasma concentration of insulin، numerically، increased، but beta hydroxyl butyrate and cholesterol declined، numerically. Replacing 240 g/kg of corn for barley in the diet caused a numerical decrease of SPC and OD as compared with other treatments. Overall، replacing corn grain for barley in the diet did not significanty affect milk production and composition. On the other hand، starch source did but only slightly affect the blood metabolites and reproductive parameters.