Research On Animal Production

     The goal of this study was to assess the effect of Insulin like growth factor-1 (IGF-1) during in vitro culture on developmental competence of bovine embryos produced from heat-stressed oocytes. In this experiment, immatured oocytes were randomly assigned into two groups and matured at 38.5 or 41 ^°C for the first 12 hours of maturation followed by 12 hours at 38.5 ^°C. After in vitro maturation and fertilization, putative zygotes in each group were randomly allocated and cultured in the presence or absence of 100 ng/ml human recombinant (hr)-IGF-1. The results showed that cleavage rate was not affected by IGF-1 and heat stress, whereas blastocyst formation rate was significantly increased by IGF-1 in the presence and/or absence of heat stress. In addition, heat stress decreased blastocyst formation rate compared to the control
(38.5 ^°C without IGF-1) group. The number of trophectoderm cells, inner cell mass and total cell number were significantly increased by IGF-1 in the presence and/or absence of heat stress. In addition, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive nuclei were significantly decreased by IGF-1 in the presence and/or absence of heat stress. Results of this experiment demonstrated that IGF-1 can improve developmental competence of bovine embryos produced from heat-stressed oocytes. It seems that IGF-1 improve bovine embryo developmental competence via increasing of total cell number and decreasing of apoptosis.
 

   Thirty multiparous Holstein dairy cows used to aim the investigation of the effects of zinc from different sources on bioavailability, production performance, and digestibility. Dairy cows in a complete randomized design randomly allocated to one of five dietary treatments that consist of 1) control (no supplement Zn), 2) Zn glycine complex (ZnGly), 3) Zn Hydroxychloride (ZnHcl), 4) Zn oxide (ZnO), 5) Zn sulfate (ZnSO4). The result indicated that different sources of zinc had not affected glucose, cholesterol and triglyceride (P>0.10). The used of different sources of zinc significantly increased of serum zinc to compare control (P<0.010).  Results showed that, BCS, milk, energy-corrected milk, fat-corrected milk yield and milk yield composition in dairy cows were not significantly affected by Zn source (P>0.10). Somatic cell count tended to decrease in ZnGly (P=0.096) and ZnHcl (P=0.073) in compare of control group. Dry matter intake was not different between treatment (P>0.10). Daily zinc intake, fecal zinc, the zinc concentration in milk per liter/or day, the zinc concentration in milk per liter/or day, apparent absorption and retention of zinc significantly were higher in zinc supplemented group in compare of control (P<0.010). Also, the used of different sources of zinc had not significantly affected on digestibility of dry matter, organic matter, and Ash (P>0.10). Therefore, the results of this study suggested that used of zinc sources in dairy cows diet ZnGly and ZnHcl have higher bioavailability than inorganic sources of zinc and also might improve milk quality throw decrease of somatic cell count.

The aim of this study was to determine the relationship between blood plasma leptin and progesterone concentrations in pre and post sexual maturity in Najdi female calves. For this purpose 7 female Najdi calves of Shushtar Breeding Station of Najdi cattle with average ages of 8 months and the average weight is 85/00±9/72 were used. For determination of the leptin and progesterone concentrations, multiple sampling before and after sexual maturity were performed. The results of this study indicate that in female Najdi calves, 13-16 month with 137.81±13.5 kg body weight was considered the age of sexual maturity. No significant correlation was found between plasma leptin and progesterone concentrations before (r=0.082, p>0.05) and after sexual maturity (r =0.096, p>0.05). There was a significantly positive correlation (r=0.73, p<0.01) between leptin concentration and body weight. Significantly positive correlation (r=0.84, p<0.01) were found between plasma leptin and age. The significantly positive correlation between plasma progesterone concentration and age (r=0.45, p<0.01) as well as body weight (r=0.44, p<0.01) were observed. In conclusion, the results showed that there was no significant relationship between leptin and progesterone concentration, but there was a positive correlation between leptin, progesterone and body weight and bud age of Najdi female calves.

Extended Abstract
Introduction and Objective: Crossbreeding of fat-tailed native sheep with well known high performance thin-tailed sheep is currently widely used as a rapid solution to enhance production and reproduction, and reduction of fat-tail of native sheep. Nevertheless, comparison studies about native and crossbred animal performance in different environment is necessary for sheep husbandry industry.
Material and Methods: This study was performed in the summer using 20 Lori-Bakhtiari (Lori) and 20 Lori-Bakhtiari×Romanov (F1) (Cross) sheep with an average weight of 31.6±2.5 kg in eight treatment with five-repetition for each in a completely randomized design with 2×2×2 factorial array including breed (Lori and Cross), water (free water and water restriction), and food (free food and food restriction). Unrestricted animals had free access to water and food, while water-restricted animals had free access to water for only one hour a day, and food-restricted animals were fed only with 0.45 to 0.65 percent of their body weight. After six weeks of treatments, lambs slaughtered and carcass traits were measured.
Results: Food restriction has widely affected the measured traits in comparsion to water and breed and significantly reduced rectal temperature, respiratory rate, water intake, final weight, carcass weight, Carcass cuts and internal organ weight, fat-tail, visceral fat, total body fat, testis weight and volume (p≤0.01), while increased the water-to-feed ratio and carcass yield without fat-tail (p≤0.007). Water restriction had lesser effects and caused a significant increase in the difference between the maximum and minimum rectal temperature in each period (p<0.05), and decrease in water consumption (p=0.0001), but had no effect on other functional, physiological, and carcass traits. Crossbreeding also significantly reduced fat-tail and total carcass (p˂0.0001), and increased visceral fat, carcass yield without fat-tail, the proportion of carcass cuts, and testis weight and volume (p≤0.01), but had no effect on other traits.
Conclusion: In general, in normal food conditions (regardless the type of access to water) crossbreed animals performed better than Lori, but there is no differencess between them in severe food restriction. Therefore, it could be concluded that in all conditions F1 generation could make the carcass healthier and reduce the generation interval due to less carcass fat and faster maturation.