Single Nucleotide Polymorphism in the Promoter Region of the IGF-1 Gene is Associated with Milk Production in Holstein and Jersey Cattle-Is the Aspect of Present Research Still Relevant in the Era of Genomic Selection?

The aim of the present study was to verify the potential effect of the C>T substitution at position-512 in the regulatory region of the IGF-1 gene on the level of milk performance traits in different cattle breeds. The study involved 227 Jersey, 147 Polish Holstein-Friesian black-and-white (HO) and 181 Polish Holstein-Friesian red-and-white (RW) cows. PCR-RFLP was used for genotyping. A bioinformatic analysis of the P1 regulatory sequence was also carried out. Three genotypes (TT, CT and CC) were identified. The CT genotype was the most frequent (0.40, 0.50 and 0.52 in Jerseys, HO and RW, respectively). The frequencies of the CC genotype were 0.22, 0.28 and 0.31 in the RW, Jersey and HO breeds, respectively, whereas those of the TT genotype were 0.19, 0.26, and 0.32 for HO, RW, and Jerseys, respectively. For Jerseys, significant differences in milk yield, fat and protein percentage were found in the second lactation. In HO, significant differences in milk fat content and yield were observed in the third lactation. No significant differences were found for RW. The bioinformatic analysis allowed us to infer that transcription factors other than the ZFP217 protein bind to the sites located outside the C>T substitution. Further studies are required to elucidate the molecular basis of the relationships observed in the present research.