مجله علوم دامی ایران
سال چهل و هشتم شماره 2 (تابستان 1396)

Understanding of population genetic structure is valuable for better implementation of breeding programs and most importantly, preservation of genetic resources. Genomic data provide an opportunity to consider complex evolutionary history of populations and reconstruct rare historical events. In this research, the structure of Iranian buffalo populations was studied by using principal component analysis and discriminant analysis principal component methods. For this purpose, the number of 404 buffalos from three breeds including North, Azari and Khozestani were sampled and genotyped by SNPChip 90k from Padano Company in Italy. The results of principal component analysis and discriminant analysis principal component showed a clear picture of the genetic structure of the studied populations. Assessing the optimal number of clusters with criteria BIC, K = 3 by the DAPC method showed the best results. The result of cross-validation for retaining principal components was optimized to 50 first components that showed the lowest MSE. In this study, DAPC predicted assignment of individuals to clusters and membership probabilities with 100% accuracy. PCA method was not able to provide a group assessment and DAPC method outperformed than PCA in achieving a clear variance difference between populations. DAPC method can be applied in quality control and stratification population correction of GWAS as an alternative to the PCA because of summarizing the genetic differentiation between groups and overlooking within-group variation and providing better population structure.

The aim of this study was to estimate the accuracy of genomic breeding values using GBLUP (Genomic Best Linear Unbiased Prediction) model and compare it with the traditional method with (BLUP) and without (BLUP_noPed) pedigree by computer simulation. In this study, a genome with 30 pairs of chromosomes, 3000 QTL and 45000 marker (SNP) was simulated. The different scenarios including two effective population of 100 and 1000 animals, two reference population size of 1000 and 2000 animals and three heritabilities, low (0.05), medium (0.30) and high (0.5) were investigated. The criteria were accuracy, bias and mean square error (MSE) of breeding value to compare traditional and genomic methods. The results showed that the accuracy of breeding values increased with increasing heritability. GBLUP mehtod was more accurate than BLUP_noPed in all scenarios and the former model had more performance in higher heritability compared with BLUP model. The accuracy of genomic breeding values decreased about 11% with increasing effective population size 100 to 1000; however, the accuracy of traditional methods was not affected by changing effective population size. Increasing the reference population size 1000 to 2000, the accuracy of genomic breeding values was improved by 5%. Although, the bias (underestimate) was higher for genomic than traditional methods in all scenario; but the MSE of breeding values was lower for GBLUP than BLUP model with increasing reference population size and heritability. Therefore, GBLUP method can be used to select top animals in populations without pedigree.

The current study was carried out to evaluate the effect of Letrozole feeding on plasma LH and FSH concentrations and testicular histology in Ross 308 broiler breeder roosters. Twenty 40-week old roosters were randomly divided into four groups, individually housed and fed different levels of capsulated Letrozole including 0 (L0), 0.5 (L0.5), 1 (L1) or 1.5 (L1.5) mg/bird/day for 12 consecutive weeks. Blood sampling was done on 1th, 3th, 5th, 7th and 9th weeks of trail. Testicular histology was assessed on samples from last week (12th) of experiment. According to the results, plasma LH and FSH levels, seminiferous tubule diameter and epithelium thickness as well as Leydig cell numbers were significantly increased in Letrozole treated groups compered to control group. The highest concentration of FSH and LH were recorded for L1 (10.39 ±0.11 and 2.93±0.08) and L1.5 (9.5±0.2 and 3.17±0.08) groups, respectively. Both L0.5 and L1 groups had significantly higher spermatogonial numbers than control group. However, blood vessel numbers were not significantly affected. In conclusion, orally feeding Letrozole (1 and 1.5 mg) could improve gonadotropin concentration and testicular histology parameters of male broiler breeders at 40 weeks of age. Further studied are needed to confirm these results and extend them to final fertility.

In the this research, 38 Holstein dairy cows (18 heads low production and 20 heads high-production) were selected randomly and blood samples were taken their from tail vein. DNA was extracted from whole blood with phenol-chloroform. PCR amplification of 750bp from 37 to 39 exons of FASN gene was performed using one pairs of special primers. Sequencing of the amplified region was performed by the Sanger method. Sequence data of other species was achieved and aligned by searching its genome database (NCBI). The nucleotide substitution rate of the sequences and molecular evolution of the FASN were calculated by maximum likelihood and neighbor-joining method, respectively and phylogenetic tree was constructed. Evolutionary and phylogenetic tree analysis was performed using MEGA6 and Dnasp5.1 softwares. Bioinformatics analysis results showed that the substitution percentage of purines was more than pyrimidine nucleotides. The numerical value of dN/dS in two groups of dairy cow and in comparison with that of other species were 1.16 and 1.12, respectively which indicating positive selection during evolution of this gene. Phylogenetic tree for the FASN gene in mammals shows close relationship between Buffalo and Bison, as well as Cats and Cheetahs (%98 and %57, respectively).The results show that over the years segregation and selection of new varieties, resulted in the development of new varieties, new proteins and also stabilizes their performance during the evolution and advance progress toward their performance has been purified.

In this study, Bayesian approach via Gibbs sampling was used to predict unknown parameters of five equivalent Genomic Best Linear Unbiased Predictions (G-BLUP), each with different scale of G matrix by using allele frequency of founder population (Gfoun), allele frequency of reference population (Gref), allele frequency equal to 0.5 (G05), a normalized matrix with average diagonal coefficients equal to 1 (Gnorm) and a weighted G matrix with A matrix (Gwei). A random mating population and a selected population were used to compare results of a trait with heritability of 0.25 on a genome constructed of three chromosomes with 105 QTLs and 3000 single nucleotide polymorphisms. The results showed that higher variance existed in the elements of G matrices compared with A matrix. Average diagonal and off-diagonal elements except Gnorm and Gwei were higher than corresponding elements in A. Gnorm-BLUP and G05-BLUP methods led to inflated genetic variance in contrast other three methods and this inflation was lower in selected population. Average accuracy over 5 G-BLUP in random population was 0.084 higher than selected population (0.762 vs. 0.652) and bias was 0.041 lower (0.026 vs. 0.04). Bias of prediction of true breeding value of selected population by using Gwei almost was zero but with Gref greater than 0.06. The greatest accuracy and the smallest bias can be obtained by using allele frequency of reference population that re-scaled with A matrix.

The aim of this research was to evaluate the effect of in ovo injection of different ratios of L- arginine to L- lysine on body growth, muscle production and blood metabolites concentration of day old Ross broilers chicks. A total of 210 fertile Ross 308 broiler breeder eggs were used in a completely randomized design with seven experimental groups of 30 individual eggs in each treatment. The experimental treatments included: sham-control (sterile distilled water injected), control (non-injected), and injection of solutions with 75.7, 80.7, 85.7, 90.7 and 95.7 percent L-arginine to L-lysine ratios. On hatching, the chicks were weighed and their blood samples were collected. Then, chicks were euthanized and their carcass traits were weighed. According to the results of this study, the maximum hatchability percentage was observed in 90.7 percent of L- arginine to L- lysine ratio. The results also showed that the in ovo injection of different L- arginine to L- lysine ratio up to 90.7 percent resulted in significant increase in chick weight (P

The effects of replacing 0, 15 and 20 of corn by percent oak acorn (OA), in diets contacting recommended and twice recommended level of methionine by NRC (1994) on performance of broilers were investigated. 528 one-day-old Cobb 500 broiler chicks in a 2×3 factorial arrangement based on completely randomized design with four replicates of 22 chicks were used. Chicks fed with diets containing 15 and 20 percent OA had lower body weight gain and higher feed conversion ratio compared to those fed with diet without OA, in all experimental periods (P