Polymorphisms in the bovine leptin promoter associated with serum leptin concentration, growth, feed intake, feeding behavior, and measures of carcass merit.

Leptin is the hormone product of the obese gene synthesized and secreted predominantly by white adipocytes. It functions as a lipostatic signal regulating BW, food intake, energy expenditure, reproduction, and certain immune system functions. Although previous studies have identified polymorphisms in the coding regions of the leptin gene in cattle that show considerable associations with feed intake, milk quality and quantity, and carcass fatness, no such associations have been reported for the leptin promoter. The current study reports associations between SNP in the 5' untranslated promoter region of the bovine leptin gene with serum leptin concentration, growth, BW, feed intake, feeding behavior, and carcass merit in hybrid cattle (n = 150). The study showed that animals with the TT genotype of a less frequent cytosine/thymine (C/ T) substitution (UASMS2; frequency of thymine allele equals 0.21) detected at position 528 in the bovine leptin promoter (GenBank Accession No. AB070368) show 48 and 39% increases in serum leptin concentration (P < 0.001), 39 and 31% increases in backfat thickness (P < 0.001), and 13 and 9% increase in marbling score (P = 0.01), compared with CC or CT genotypes, respectively. Animals with the TT genotype also show significantly higher feed intake (P < 0.001), growth rate, metabolic BW (P < 0.05), and live weight at slaughter (P < 0.10). Animals with the GG genotype of a more frequent cytosine/guanine (C/G) substitution (UASMS3; frequency of G allele equals 0.59) at position 1759 in the bovine leptin promoter (GenBank Accession No. AB070368) also show higher feed intake (P = 0.001), growth rate (P < 0.10), and BW (P < 0.01). The thymine allele of UASMS2 and the guanine allele of UASMS3 were separately associated with higher feeding duration (P < 0.05). The two SNP show significant linkage disequilibrium and could also be relevant in predicting other characteristics, such as milk yield and quality in cattle. These results, however, represent the initial associations of the polymorphisms with these traits, and further efforts are required to validate these findings in other populations.