Identification of genetic variants of bGH, GHR and IGF1 gene and their association with lactation persistency in Tharparkar cattle

Persistency can be explained as number of days during which the high level of milk production is maintained after the peak milk yield. The aim of this study was to identify genetic variants of bovine -Growth Hormone (bGH), Growth Hormone Receptor (GHR) and Insulin like Growth Factor1 (IGF1) gene and their association with lactation persistency in Tharparkar cattle. Study was carried out using data of daily milk yield, monthly test days, total milk yield and peak yield of 372 lactation records of 190 Tharparkar cattle maintained at Livestock Research Centre of ICAR-National Dairy Research Institute from 1996-2019. Lactation persistency was estimated using Woods and Wilminks method and its least squares means were 2.37 +/- 0.08 and -5.4 +/- 0.56, respectively. Investigations on polymorphism were performed using seven reported primers for amplifying targeted regions of bGH, GHR and IGF1 gene. In PCR-RFLP, bGH-MspI RFLP had shown polymorphism in intron 3 and its genotypic frequencies were TT 0.49, CT 0.39 and CC 0.12. The allelic frequency of C and T were 0.31 and 0.69, respectively. The bGH-AluI RFLP had shown monomorphism in exon 5. GHR-AluI had shown polymorphism in exon 10 with only two genotypes AA and AG with frequency of 0.92 and 0.08, respectively. The frequency of A and G allele was 0.96 and 0.04, respectively. In GHR-StuI and IGF1-TasI in promoter region, RsaI in exon 3 and SnaB I in exon 1 had shown monomorphism. No significant association was found between genetic variants of bGH and GHR with lactation persistency in Tharparkar cattle.