Allelic and Genotypic Frequencies of the Leptin Gene Sau3AI-Restriction Fragment Length Polymorphism and Evaluation of Its Association with Age at Puberty in Cattle in the Southwestern United States and Northern Mexico

Abstract

Leptin is a hormone secreted by adipose tissue that influences appetite, growth, and reproduction. In cattle, the leptin gene contains a Sau3A-restriction fragment length polymorphism (RFLP) within intron II and exon III. This RFLP yields two alleles (A and B) and three genotypes (AA, AB, and BB). Because level of adiposity is important to numerous performance traits, two studies were conducted to assess the potential use of the leptin Sau3AI-RFLP as a selection tool in cattle in the Southwestern United States and Northern Mexico. The objective of the first study was to survey allelic and genotypic frequencies of the Sau3AI-RFLP in breed groups of cattle selected for beef production. High frequencies (≥0.76) of the A allele were observed in cattle that were Bos taurus (Angus and Criollo), Bos indicus-influenced (Brangus, Brahman, F1-Hereford x Brahman, Santa Cruz, and Santa Gertrudis), and of historic lineage of Bos taurus x Bos indicus (African Mashona). Genotypic frequencies in these breed groups were 0.82 (AA), 0.16 (AB), and 0.02 (BB). The objective of the second study was to evaluate the relationship of the leptin RFLP to age at puberty in heifers. No relationship was detected (P < 0.38) between genotype and age at puberty. The A allele existed in the breed groups evaluated with high frequency, thus negating the ability to assess the relationship of the B allele to age at puberty. Findings do not support use of the leptin Sau3AI-RFLP as a marker in selection strategies for cattle in the Southwestern United States and Northern Mexico.