Association of lactation persistency with genetic variants of bovine growth hormone gene in Indian Sahiwal cows

The aim of this study was to determine the associations of persistency with genetic variants of bovine growth hormone (bGH) gene in Indian Sahiwal cows. The data pertaining to the monthly test day milk yield (MTDMY) and first lactation length (F1,14 of 305 lactating Sahiwal cows over a period of 23 years (1993-2016) were subjected to analysis. Persistency of milk yield was estimated by using test day based ratio method and Wilmink b function. Mean LL was 220.06 +/- 8.15 days in all studied Sahiwal cows, however, 276.67 +/- 10.25 days in cows with >= 100 days of LL and having 500 kg MY. The peak of milk yields was achieved at third TD of the first lactation. Macrophage stimulating protein I (MspI) and Arthrobacter luteusl (Alul) restriction endonucleases were used to digest the amplified regions in intron 3 and exon 5, respectively of bGHgene. The bGHMspI restriction fragment length polymorphism (RFLP) yielded TT. CT and CC genotypes, whereas bGH-AluIRFLP yielded CC. CG and GG genotypes. Significant association was found between first lactation persistency estimated using test day based ratio method and bGH-MspI polymorphism. No significant association was found between first lactation persistency and bGH-AluI polymorphism. In summary. results of present study revealed that the TT genotype of bGH-MspI gene in Sahiwal cows has better lactation persistency than other genotypes.