Association between single nucleotide polymorphism in the ovine DGAT1 gene and carcass traits in two Iranian sheep breeds.

The aim of the study was to investigate the single nucleotide polymorphisms (SNPs) at 16-17 exon of DGAT1 gene in Lori-Bakhtiari sheep (LB) and Zel sheep (Z) breeds and provide a foundation for studying the relationship of DGAT1 gene with some carcass traits and the genetic relationship between LB sheep and Z sheep breeds. A total of 309 sheep were slaughtered and the carcass weight, backfat thickness, fat-tail weight, fat-tail percentage, dressing percentage, and dressing percentage adjusted to fat-tail weight were measured. Single nucleotide polymorphism was detected by comparing sequences of PCR products, and the restriction fragment length polymorphism (RFLP) technique was adopted for genotyping. The results of PCR-RFLP analysis showed that the SNP had three genotypes of TT (272 and 37 bp), TC (309, 272, and 37 bp), and CC (309 bp), in which TT was the predominant genotype and allele T was predominant allele in LB and Z sheep breeds. At the DGAT1 locus, CC sheep showed the significantly greater fat-tail weight (P < 0.05) and backfat thickness (P < 0.01). The results of this study demonstrate novel associations in which the C allele had a positive effect on fat-tail weight and backfat thickness in fat-tailed sheep.

Direct and maternal (co)variance components, genetic parameters, and annual trends for growth traits of Makooei sheep in Iran.

Genetic parameters and genetic trends for birth weight (BW), weaning weight (WW), 6-month weight (6MW), and yearling weight (YW) traits were estimated by using records of 5,634 Makooei lambs, descendants of 289 sires and 1,726 dams, born between 1996 and 2009 at the Makooei sheep breeding station, West Azerbaijan, Iran. The (co)variance components were estimated with different animal models using a restricted maximum likelihood procedure and the most appropriate model for each trait was determined by Akaike's Information Criterion. Breeding values of animals were predicted with best linear unbiased prediction methodology under multi-trait animal models and genetic trends were estimated by regression mean breeding values on birth year. The most appropriate model for BW was a model including direct and maternal genetic effects, regardless of their covariance. The model for WW and 6MW included direct additive genetic effects. The model for YW included direct genetic effects only. Direct heritabilities based on the best model were estimated 0.15 ± 0.04, 0.16 ± 0.03, 0.21 ± 0.04, and 0.22 ± 0.06 for BW, WW, 6MW, and YW, respectively, and maternal heritability obtained 0.08 ± 0.02 for BW. Genetic correlations among the traits were positive and varied from 0.28 for BW-YW to 0.66 for BW-WW and phenotypic correlations were generally lower than the genetic correlations. Genetic trends were 8.1 ± 2, 67.4 ± 5, 38.7 ± 4, and 47.6 ± 6 g per year for BW, WW, 6MW, and YW, respectively.

Monthly variation of plasma concentrations of testosterone and thyroid hormones and reproductive characteristics in three breeds of Iranian fat-tailed rams throughout one year.

Nine sexually mature rams, three Shall, three Afshari and three Zandi were used in this study. Semen of rams was collected twice per month during the four seasons of the year and blood samples were obtained via jugular vein. Seminal characteristics, scrotal dimension and blood parameters were measured at 2 week intervals. Time of the year significantly (p < 0.05) affected the volume of semen, sperm concentration, percentage live sperm, percentage abnormal sperm, sperm mass motility, total sperm number, scrotal circumference, relative testis volume and serum levels of testosterone, triiodothyronine and thyroxine. All of semen characteristics, except sperm abnormality, were high in summer months than at other months of the year (p < 0.05). Sperm abnormality was higher in autumn months (p < 0.05). Relative testis volume and testicular circumference were higher in autumn and summer months than at other mouth of the year, respectively (p < 0.05). Scrotal circumference were not significant between Shall and Afshari breeds but comparison with Zandi breed, Scrotal circumference was bigger (p < 0.05). The largest values for thyroid hormones synchronized with low reproductive performance of rams, but testosterone was highest levels at this time (p < 0.05). TimexBreed interaction effect was significant for sperm concentration, total sperm number, semen volume, testis circumference, relative testis volume, thyroid hormones and testosterone (p < 0.05).