Relationship between SCD1 Gene Polymorphism and the Production and Composition of Milk in the Iraqi Awassi Sheep.

Selection based on genetic makeup became an important tool in genetic improvement. The development of molecular biology opened the way to study the genes of farm animals and genetically improve them. The aim of this study was to determine the Allele frequency and genotype distribution of the SCD1 gene and its relationship to milk production and its main components from fat, protein, lactose and non-fat solids percentage in Iraqi Awassi sheep. Fifty-one female Awassi sheep were used in this study. The genotype distribution of the SCD1 gene in the studied Awassi sheep sample was 50.98, 41.18 and 7.84% for each of the CC, CA and AA genotypes, and the discrepancy between these percentages were highly significant (P≤0.01), and the appearance of the C and A alleles with a frequency of 0.72 and 0.28 respectively, highly significant differences (P≤0.01) appeared in the total milk production according to the genotype. As for the milk components, it was found that there were significant (P≤0.05) differences in the percentage of fat and the percentage of non-fat solids. From the results of the current study, it can be concluded that the SCD1 gene can be adopted as an important indicator in developing genetic improvement strategies for Awassi sheep to maximize the economic return from breeding projects by selecting and cross-breeding the genotypes that achieved the best product performance.

Comparison of several methods of sires evaluation for total milk yield in a herd of Holstein cows in Yemen.

A total of 956 lactation records of Holstein cows kept at Kaa Albon station, Imuran Governorate, Yemen during the period from 1991 to 2003 were used to investigate the effect of some genetic and non-genetic factors (Sire, parity, season of calving, year of calving and age at first calving as covariate) on the Total Milk Yield (TMY), Lactation Length (LL), and Dry Period (DP). Components of variance for the random effects (mixed model) were estimated by Restricted Maximum Likelihood (REML) methodology. Sires were evaluated for the TMY by three methods, Best Linear Unbiased Prediction (BLUP) using Harvey program, Transmitting Ability (TA) according to the Least Square Means of sire progeny (TALSM) and according to Means (TAM). Results showed that TMY and DP were affected significantly (P < 0.01) by all factors except season of calving and age at first calving, while LL was affected significantly (P< 0.01) only by year of calving and parity. The averages of the TMY, LL, and DP were 3919.66 kg, 298.28 days, and 114.13 days respectively. The corresponding estimates of heritability (h(2)) were 0.35, 0.06, and 0.14 respectively. The highest and lowest BLUP values of sires for the TMY were - 542.44 kg and 402.14 kg, while the corresponding estimates for TALSM and TAM were - 470.38, 380.88 kg and - 370.12, 388.50 kg respectively. The Spearman rank correlation coefficients among BLUP, TALSM and TAM ranged from 0.81 to 0.67. These results provide evidence that the selection of sires will improve the TMY in this herd because of the wide differences in genetic poetical among sires, and a moderate estimation of heritability.