Leptin Genotype Is Associated with Lactation Performance and Health of Holstein Cows

The objectives were to evaluate the associations among single nucleotide polymorphisms (SNP) in the R4C locus in exon 2 of the leptin gene and the lactational performance and health of Holstein cows. Eight hundred and fourteen lactating dairy cows had their DNA sequenced in exon 2 of the leptin gene to determine the presence of SNP in the R4C locus. Cows were milked 3 times daily, and yields of milk and milk components were recorded monthly individually during the first 305 d of lactation. Cows were examined daily by herd personnel for diagnosis of health events such as retained fetal membranes, displacement of abomasum, lameness, and mastitis. Resulting genotypes were CC (34.6%), CT (48.2%), and TT (17.2%). Cows bearing the CT genotype had lower body condition (2.98 ± 0.02) during the first 62 d in milk (DIM) than cows homozygous for the C (3.02 ± 0.02) and T (3.04 ± 0.03) alleles. Leptin genotype was associated with yields of milk and milk components, and cows homozygous for the C allele were less productive than those carrying the CT and TT genotypes. The 305-d yields of 3.5% fat-corrected milk, milk fat, and milk true protein were less in CC compared with CT cows by 258, 12, and 10.7 kg, respectively. Cows carrying the TT genotype had increased incidence of displacement of abomasum (4.3%), but genotype did not affect the incidence of retained fetal membranes, clinical and subclinical mastitis, or lameness. Risk of developing at least one clinical health disorder was influenced by leptin genotype, and cows carrying the CT genotype had the lowest risk for developing any disease (19.6%). Mating decisions to increase the frequency of cows heterozygous in the R4C locus may improve productivity and health.