Association of single nucleotide polymorphisms in genes coding insulin-like growth factor 1 system and milk production traits in Montbeliarde cows

Abstract

The insulin-like growth factor 1 system plays a central role in the growth and  development of the mammary gland. Insulin-like growth factor 1 (IGF1) and  insulin-like growth factor 1 receptor (IGF1R) have been proposed as candidate  genes for milk production traits. This study involved a population of 163  Montbeliarde cows. Five polymorphic sites were analysed using the polymerase  chain reaction: restriction fragment length polymorphism (PCR-RFLP) (TaiI and  MspI restriction enzymes) and amplification-created restriction site (ACRS) (SnaBI, TasI and TaqI restriction enzymes). The frequencies of the most common alleles were 0.67 for the T allele (IGF1/SnaBI), 0.85 for the A allele (IGF1/TasI), 0.95 for the C allele (IGF1R/TaiI), 0.84 for the G allele (IGF1R/MspI) and 0.69 for the G allele (IGF1R/TaqI). In the first lactation, IGF1/TasI polymorphisms and all single nucleotide polymorphisms in the IGF1R gene were associated with differences in milk, fat and protein yields, without further confirmation in the second lactation. No differences were found in milk production traits between IGF1/SnaBI genotypes and combined genotypes. To date, this is the first association study based on polymorphisms of the primary genes encoding the IGF-1 system in a small herd of Montbeliarde cows. If specific haplotypes could be determined in large-scale studies, based on Montbeliarde and other dairy breeds, it would provide a valuable genetic tool to identify causative mutations.
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Keywords: IGF1, IGF1R, milk production traits, polymorphism