Single nucleotide polymorphisms at the imprinted bovine insulin-like growth factor 2 (IGF2) locus are associated with dairy performance in Irish Holstein-Friesian cattle

Abstract

The imprinted insulin-like growth factor 2 gene (IGF2) encodes a fetal mitogenic hormone protein (IGF-II) and has previously been shown to be associated with performance in dairy cattle. In this study we assessed genotype-phenotype associations between four single nucleotide polymorphisms (SNPs) located within the bovineIGF2locus on chromosome 29 and a range of performance traits related to milk production, animal growth and body size, fertility and progeny survival in 848 progeny-tested Irish Holstein-Friesian sires. Two of the four SNPs (rs42196909andIGF2.g-3815A>G), which were in strong linkage disequilibrium (r2=0·995), were associated with milk yield (P⩽0·01) and milk protein yield (P⩽0·05); thers42196901SNP was also associated (P⩽0·05) with milk fat yield. Associations (P⩽0·05) with milk fat percentage and milk protein percentage were observed at thers42196901andIGF2.g-3815A>GSNPs, respectively. Thers42196909andIGF2.g-3815A>GSNPs were also associated with progeny carcass conformation (P⩽0·05), while an association (P⩽0·01) with progeny carcass weight was observed at thers42194733SNP locus. None of the four SNPs were associated with body size, fertility and progeny survival. These findings support previous work which suggests that theIGF2locus is an important biological regulator of milk production in dairy cattle and add to an accumulating body of research showing that imprinted genes influence many complex performance traits in cattle.