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.
"Experientia docet" - Experience is the best teacher