فصلنامه تحقیقات تولیدات دامی
سال دوم شماره 2 (تابستان 1392)

This experiment was conducted to study the effect of induced transient hypothyroidism on pubertal initiation, histological traits of testis and semen quality in breeder roosters. A total of sixty-six broiler breeder male chicks were randomly assigned to two experimental groups of control or hypothyroidism in a completly randomized design with three pens per group. In hypothyroidism group, chicks were fed dietary treatment of 0.1% propylthiouracil from 6 to 12 week of age. Body weight, thyroxin and testosterone concentrations were measured at 3-week intervals from 6 to 18 and also at 26 week of age. Histological caracteristics and the expression of connecxin 43 gene in testis were assayed in experimental groups and semen quality was evaluated for 10 weeks after photostimulation. Connexin 43 gene expression was higher in control group (1.181) than hypothyroidism one (0.782) at 18 week of age (P<0.05) and was similar at 26 week of age (P>0.05). Semen volume was greater in hypothyroidism group (0.46 ml) than that of control one (0.39 ml). Also, sertoli cell number was greater in hypothyroid group at 18 (159.9 /mm2) and 26 (165.9 /mm2) week of age than that in control group (P 0.05). Also, relative testis weight was greater in hypothyroidism group (749 mg/100gBW) than control group at age 26 week of age (P<0.05). Therefore, addition of propylthiouracil in breeder male chicks diet in prepubertal period, probably resulted in higher sertoli cell number and testicular weight via delay in puberty.

The present study was conducted to evaluate some oxidative stress in ram Sertoli cells under heat stress condition. The testis of 10 ram lambs was gathered from abattoir (during 5 times) and transferred to laboratory for isolation and culture of Sertoli cells. Isolated cells from lamb testes were divided into 3 plates and maintained in temperatures 32 ºC (control), 39 ºC (mild stress) and 42 ºC (severe stress) for 6 hours. The percentage of cell viability, the amount of lipid peroxidation (TBARS), the antioxidant capacity (FRAP) and superoxide dismutase activity were measured in all groups after 6 hours. The percentage of alive cells were reduced in group 42 ºC (78 ± 6.8) as compared to control (95 ± 9.3; P<0.05). Lopud neroxidation was higher in sever stress (0.6 ± 0.06) than control (0.46 ± 0.05; P<0.05). In conclusion, heat stress could be a detrimental factor for viability of Sertoli cells via increasing of lipid peroxidation.

The objective of this study was to determine the optimal herd life of dairy cows in North West of Iran based on data collected from nine large herds of three provinces (Ardabil, East Azerbaijan and West Azerbaijan) and to assess its affecting factors using data on costs and revenues in 2012 and by stochastic dynamic programming. Variables used to describe the state of cows included lactation number at 10 levels, production ability at 3 levels and reproductive performance at 4 levels. Markov chain was used to incorporate the probability for each level of factors in determining the status of a cow. The objective function was the expected net present value of a cow in a 10-years horizon and the optimization criterion was to maximize this function. Using dynamic programming the optimal combination of the state variables was realized and hence the optimum herd life of the cows was estimated to be 4.99 years. Examination of optimal objective function in different states revealed that increasing the production level and reducing the calving interval resulted in higher expected net present value of cows. The effect of changes in price of heifers, milk and discount rates on optimal herd life was examined and it was found that by increasing heifer price, lowering milk price and increasing the discount rate, the culling rate was decreased and optimal herd life was increased.

The aim of the present trial was to investigate the effects of zinc oxide (ZnO) and nano zinc oxid (nZnO) on performance and some blood parameters of Markhoz goat kids. A total of 30 male Markhoza goat kids aged 6-7 months (191.95 ± 6.40 days) in a completely randomized design were allocated into five treatments including zero, 20 and 40 ppm zinc from ZnO source and 20 and 40 ppm zinc from nZnO source and fed with a basal diet (containing 22.12 mg Zn/kgDM) for 70 days. Animals were weighed fortnightly and blood samples were taken at first day and days 35 and 70 for measurement of blood parameters. Dry matter intake and average daily gain in all treatments were not significant difference. Digestibility of dry matter and nutrients in the diet also were not affected by zinc supplementation. There was no significant difference between treatments for blood parameters (glucose, urea, albumin and total protein, alkaline phosphatase and lactate dehydrogenase enzymes and vitamin A levels). Zn supplementation did not affect plasma Zn concentration of the animals except on day 35. In conclusion, the results showed that the levels of 20 and 40 ppm zinc from ZnO and nZnO sources had no effect on performance and blood parameters of Markhoz goat kids fed a diet containing 22.12 ppm zinc.

To investigate the effects of Zataria multiflora Boiss essential oil on performance and oxidative stability of meat of broiler chicks, an experiment was conducted with 500 one-day-old chicks as completely randomized design with 5 treatments (control, basal diet with 100 mg/kg probiotic, basal diet with 150 mg/kg avilamycine, and basal diet with 200 or 400 mg/kg Zataria multiflora Boiss essential oil), 4 replicates and 25 chicks per replicate for 42 days. Results indicated that the main compounds of Zataria multiflora Boiss essential oil were thymol (22.3%), p-cymene (14.2%), linalool (6.2%), γ-terpinene (6.4%), 1,8-Cineol (5.3%), and carvacrol (3.1%). Adding Zataria multiflora Boiss essential oil to the diet had no significant effect on body weight, feed conversion ratio, livability, and production index (P>0.05); while, feed intake to 42 days of age and body weight to 28 days of age in antibiotic treatment was higher than the other groups (P<0.05). The relative weight of the carcass and different parts of carcass and abdominal fat were not affected by experimental treatments (P>0.05).Amount of thiobarbituric acid reactive substances (TBARS) in thigh meat stored for 90 days after slaughtering was lower in thyme-fed groups compared to those fed antibiotic (P<0.05), but the effect was not significant compared to the control. According to the results, although use of Zataria multiflora essential oil interm of functional was not effective as antibiotic, but its active compounds with antioxidant property had favorable effect on the oxidative stability of meat in a long time so it would be considered for storing meat in fridges.

This experiment carried out to determination of the chemical composition and degradability of sorghum silage at two maturity stage. Sorghum forage harvested at two maturity stage being vegetative and bloom. The chopped forages were ensiled in mini- silo for 81 days. The silages were tested for chemical composition and degradation characteristics of dry matter, crude protein and neutral detergent fiber. The nylon bags method was used for determination of the sorghum silage degradability. The results showed, with increasing maturity, content of crude protein (8.54 to 6.90 %DM), total tannins (1.48 to 0.18 %DM), water soluble carbohydrates (19.72 to 11.35 g/kg) and calcium (0.059 to 0.049 %DM) of sorghum silage significantly decreased (p < 0.05). The amount of neutral detergent fiber content (NDF), acid detergent fiber content (ADF), ether extract, ash, condensed tannins, sodium, phosphorus and potassium were not significantly different amongtreatments. The degradability of dry matter, crude protein and NDF increased with advancing maturity stage, but degradation parameters (section of quickly and slowly degradation) were not significantly different at two maturity stage. It is concluded, sorghum forage harvested at vegetative stage was more beneficial than the bloom stage for ensiling.

The present study was investigated two different nitrogen sources (soybean meal and urea), accompanying with two different barley grain levels on nutrients digestibility, rumen pH and rumen ammonia nitrogen in sheep nutrition. Four rumen cannulated sheep with 4 months ages and averaging BW 35.5 ± 1.4 kg were allocated in a 4×4 change over design. Experimental diets were as: 1- 38.96% barley grain with urea, 2- 49.05% barley grain with urea, 3- 29.58% barley grain with soybean meal and 4- 40.65% barley grain with soybean meal. The results showed that rumen pH was differed among treatments on 2 and 5 h after feeding (P< 0.05). The results showed that the greatest pH value was for treatment 1 (6.50) on h 2 and the lowest was for treatment 2 5.98) on h5 after feeding. The concentration of rumen ammonia also was differed among treatments in all sampling times except than of for h 5 after feeding (P< 0.05). The OM and cell wall digestibilities were significantly differed among treatments which the greatest digestibility of OM and cell wall were for treatments 4 (66.8%) and 3 33.6%), respectively (P< 0.05). Overall, it could be concluded that the rumen ammonia concentration was influenced by both protein source and barley level feeding and using soybean meal caused to less ammonia nitrogen concentration in rumen. Moreover, nutrients digestibility was influenced by nitrogen sources and hence digestibility values were highest in diets containing soybean meal.