Sequence Variations in the Bovine IGF-I and IGFBP3 Genes and Their Association with Growth and Development Traits in Chinese Beef Cattle

The objective of this study was to determine the genotype effects of the bovine insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP3) genes on growth and development traits in beef cows, including 130 Chinese Simmental, 42 Nanyang, and 47 Luxi Yellow cattle. Sequence variations in the bovine IGF-I and IGFBP3 genes were investigated by single strand conformation polymorphism (SSCP). SSCPs were detected in 6 fragments, which is the 5′-flanking region, the 2nd exon, the 5th exon, and the 5th intron of the IGF-I gene, and the 2nd exon, the 3rd exon of the IGFBP3 gene. Two polymorphisms, an A-to-G transition in the 2nd exon of the IGF-I gene and a T-to-C transition in the 2nd exon of IGFBP3 gene were detected in 3 breeds. The allele frequencies of 2 polymorphisms were 0.0411 (A), 0.9589 (B), and 0.7237 (A), 0.2763 (B), respectively. These 2 loci were analyzed to associate with body weight, height at withers, body length, heart girth, rump width, and beef production index (BPI) at 0, 6, 12, 24, and 36-month old. The IGFBP3 locus was shown to be associated with rump width, heart girth at 24-month and 36-month. Animals with BB genotype had higher rump width (24.86 ± 0.47) cm at 24-month and (27.50 ± 0.63) cm at 36-month. The heart girth was highest for the individuals with BB genotype (171.33 ± 1.84) cm and higher than those with AB genotype (166.68 ± 1.13) cm (P < 0.05) at 36-month.