Analysis of selection effect based on kappa casein gene on milk yield production of Iranian Sarabi cattle breed using stochastic simulation.

PCR-RFLP was used to genotype 87 Sarabi native cattle of north-western Iran for A and B alleles of kappa casein gene. A 350 bp length of exon 4 and intron 4 was amplified and digested with HinfI endonuclease. Samples were loaded on agarose gel (2%) and genotyped under UV light. Allele frequency of desirable B allele was 0.57. Stochastic simulation was used to generate milk yield trait for a population of 4950 females and 50 males for 15 overlapping generations. Population parameters included 1100 and 436 kg for average milk yield and phenotypic deviation, respectively; with heritability of 0.27. Additive and dominance effects of Kappa Casein gene were considered as 187.63 and 50.37 kg, respectively. Two methods were considered for selection of males based on the first phenotypic record of their dams (PAS) or molecular information of each male, individually (GAS). Females were always selected on their first phenotypic record. Although, there was a significant difference between polygenic and major gene genetic response between two methods after the 5th generations, but there was no significant difference for the sum of polygenic and major gene response. After 15 generations of selection there was no significant difference between inbreeding coefficient under two methods. Selection plan for males based on one single major gene had no advantage over the conventional selection based on dam record in native Sarabi breed.

Polymorphism of the bovine POU1F1 gene: allele frequencies and effects on milk production in three Iranian native breeds and Holstein cattle of Iran.

The aim of this study was to estimate the allele frequencies in polymorphic site of exon six of POU1F1 gene in three Iranian native and Holstein cattle. Genomic DNA was extracted from 3 Iranian native cattle breeds, including 97 Mazandarani, 87 Sarabi, 112 Golpaygani and also 110 Holstein cattle. A 451 bp fragment of intron 5 and exon 6 were amplified and digested with HinfI restriction enzyme. Frequencies of allele A were 0.37, 0.27, 0.34 and 0.21 for Mazandarani, Sarabi, Golpaygani and Holstein cattle, respectively. Significant differences in genotype frequencies were found between Mazandarani or Golpaygani and Holstein cattle. No significant differences in genotype frequencies were found between Sarabi and Holstein cattle. Transition A to G in nucleotide 1256 is responsible for HinfI(-) allele. No significant association was observed between POU1F1 polymorphism and milk production. Differences in allelic frequency between native Bos indicus breeds (Mazandarani, Golpaygani) and Holstein at the present study might be due to differences in origin breeds, low number of samples and/or as the effect of natural selection in native breeds.