Association of IGF1R Gene Polymorphisms with Growth Traits in Yak

This study investigated polymorphisms in the insulin-like growth factor 1 receptor (IGF1R) gene and their associations with growth traits in yak. A total of 400 three-year-old female yaks were evaluated for body weight, withers height, body length, chest circumference, and cannon circumference. Four single-nucleotide polymorphisms (SNPs) were identified in the amplified region of exon 13 by PCR amplification followed by direct Sanger sequencing. Three loci exhibited moderate polymorphism and deviated from Hardy–Weinberg equilibrium, whereas g.7383182G>A showed low polymorphism and was in equilibrium. The CC genotype at g.7383089C>T was associated with significantly higher body weight, body length, and chest circumference than the CT and TT genotypes. The GA genotype at g.7383141G>A showed favorable values for several growth traits. At g.7383142T>C, the TT genotype showed higher body weight, body length, and chest circumference than the CC genotype. The GG genotype at g.7383182G>A was associated with greater withers height than the GA genotype. Seven common haplotypes were identified, with Hap4 being the most frequent (0.335). The H4H1 diplotype showed relatively favorable overall growth performance. These findings suggest that IGF1R variants may be candidate markers for yak growth traits, but validation in larger, independent populations is required.