The Association of Four Polymorphisms within the Insulin-Like Growth Factor 1 Receptor Gene with Milk Production Traits in Simmental Cows

The aim of this study was to determine the frequency of alleles and genotypes of four polymorphisms located in exons 2, 10 and 16 of the gene encoding insulin-like growth factor type 1 receptor (IGF1R) in the tested herd of 242 Simmental cows and to search for the relationship between these polymorphisms and selected milk production traits. The study applied the following methods: PCR-RFLP and combination of nested PCR and ACRS-PCR. The presence of three genotypes was found for all SNPs. The frequency of alleles was as follows: C - 0.29 and T - 0.71 (IGF1R/e2/MspI), A - 0.33 and G - 0.67 (IGF1R/e2/TaqI), C - 0.77 and T - 0.23 (IGF1R/e10/MspI) and C - 0.53 and T - 0.47 (IGF1R/e16/RsaI). In all lactations, cows with TT (IGF1R/e2/MspI) and GG genotypes (IGF1R/e2/TaqI) produced the highest amounts of milk, fat and protein (P≤0.01), particularly individuals with the combined TT/GG genotypes. As regards the IGF1R/e10/MspI and IGF1R/e16/ RsaI genotypes, the highest milk, fat and protein yields were observed in cows with separate and combined CC/CC genotypes, while the lowest in animals with combined TT/TT genotypes. Cumulative analysis of all genotype combinations showed that individuals with a potentially best combination of TT/GG/CC/CC might be characterized by the highest milk yield as well as fat and protein content in milk. Potentially unfavorable combinations (such as CC/AA/TT/TT and similar) have been almost completely eliminated from the herd tested. The IGF1R gene is proposed as a candidate gene for milk traits in cattle.