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.