Plant, Animal & Microbe Genomes X Conference

January 12-16, 2002
Town & Country Convention Center
San Diego, CA

Workshop: Cattle/Sheep
            

EFFECTS OF A BOVINE LEPTIN MISSENSE MUTATION ON ANIMAL PERFORMANCE.

¹ Department of Animal and Poultry Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada.

Leptin is the hormone product of the obese gene. Leptin is secreted predominantly by adipocytes and modulates appetite and energy metabolism. A SNP was identified in the sequence of exon two between animals that had either high or low total body fat measurements. This C to T transition causes a non-conserved amino acid substitution from arginine to cysteine. Using a purposeful mismatch in the reverse primer, a Kpn2I recognition site was introduced where the C allele is cleaved. This PCR-RFLP was amplified in beef breeds of cattle. The effects of the SNP genotypes on carcass fat measurements were analyzed by analysis of variance with the fixed effect of breed included in the model. Both average fat and grade fat are significantly affected by genotype (P = 0.023 and P = 0.013 respectively). The T allele was associated with fatter and the C allele with leaner carcasses. Crossbred feedlot steers were selected based on SNP genotype (TT or CC). They were finished to either 8 or 12 mm of backfat depth as determined by ultrasound. Animals homozygous for the T allele reached the targeted backfat depth with fewer days on feed and at lighter weights. A ribonuclease protection assay was developed to quantify leptin mRNA. Animals homozygous for thymine expressed higher levels of leptin mRNA. This may suggest that the T allele imparts a partial loss of biological function. We are currently evaluating this SNP in dairy cattle for an association to milk composition or efficiency of milk production.