Study on second intron of prolactin gene polymorphism and its association with milk yield in Kurdi sheep of Shirvan

This study was conducted to investigate association between prolactin gene polymorphism and milk yield of Shirvan Kurdi sheep. Prolactin is a lactogenic hormone that plays a significant role in milk production; its depletion in sheep provokes a severe reduction of milk secretion suggesting that prolactin is a functional candidate gene that could contribute to variations in milk yield. An Investigation indicated that polymorphism prolactin gene in Chios sheep. They identified a 23-bp indel (insertion or deletion) in the 213 region and found that the B allele is the result of a 23-bp deletion in a allele. They also reported A and B allele with the frequencies of 0.71 and 0.29, respectively and foundthat the B allele may be associated with higher milk yield. The present study investigated the association between polymorphisms in prolactin gene and daily milk yield records of Kurdi ewes in Hossien Abad Kurdi sheep breeding station.
In this study, blood samples were collected randomly from 100 milking Kurdi ewes in Hossien Abad Kurdi sheep breeding station. Milking was carried out by hand combined with lamb suckling at 14 days intervals starting from May to Agust 2012.Allele and genotype frequencies, chi-square test and the goodness of fit test for Hardy–Weinberg equilibrium were calculated with PopGeneV 1.31 software. Statistical Analysis was performed using INBREED and the MIXED procedures of SAS to estimate the association of genotypes with milk production.
A 23-bp indel (insertion or deletion) was identified in prolactin gene by PCR.A mixed model was used to investigate the association of prolactin gene with test day milk yield. AA genotype had the highest genotype frequency in the studied population (0.60).A and B allele frequencies were 0.765 and 0.235, respectively. Results indicated that there was no significant association between prolactin gene polymorphism and milk yield in the studied population.
In the present study, no genotype was identified to be better than the others and there was no significant association between prolactin gene polymorphism and milk yield.