Influence of obesity gene in quantitative traits of swine

Abstract

Genotype data of 477 animals of several swine races (Landrace - LD, Large White - LW, Pietrain - PI, LWXLDXPI, Piau, Monteiro, and unknown race) were obtained to determine the allele frequency of the obesity gene. Genotype data of 174 crossbred swine (LWXLDXPI) were also obtained, in order to assess its correlation with carcass evaluation data (lean meat percentage, backfat thickness at P2, loin eye area, adjacent fat area, total fat and meat). Finally, genotype data of 96 pure swine (Landrace, Large White and Pietrain) were collected, to establish its relation with meat quality (drip loss, meat color, texture analysis and intramuscular fat) and carcass evaluation data (lean meat percentage; ham, loin, shoulder and belly weights; and backfat thickness at P2). This work also aimed associating EPDs (expected progeny differences) for litter size, daily weight gain and backfat thickness with genotype data of 49 Large White males and 54 Landrace females. Genotyping was done on animal blood by PCR-RFLP, based on Stratil et al. (1997). Statistical analysis was done by using SAS software for variance analysis between genotypes and data for each cited class. For purebred animals, a mixed model was used, with sire within race as random effect. The allelic frequencies of alleles T and C were, respectively: 0.8142; 0.1857 (Landrace); 0.9125; 0.0875 (Large White); 0.9433; 0.0566 (Pietrain); 0.8333; 0.1666 (LWXLDXPI); 0.2500; 0.7500 (Piau); 0.8750; 0.1250 (Monteiro), and 0.8870; 0.1130 (unknown race). Since the highest allele C frequency occurred in Piau, we suggest that this allele could be associated with fat accumulation. In the Landrace race, a study was done separating the frequencies of 2 generations (great-grandfather and grandfather), and the differences confirmed by a Chi-square test, a higher frequency of allele C having been found in the grandparental generation. This suggests that this allele could be eliminated by selection from the great-grandparental generation, when the male grandparent is replaced by the great-grandparental generation. The obesity gene did not influence any of the carcass evaluation data from crossbred animals. In pure swine, where the only genotypes were TT and TC, it greatly influenced shoulder weight and meat texture, with the highest average in heterozygotes (shoulder: 4.07 vs. 3.93; texture: 2.62 vs. 1.82), suggesting better carcass quality and worse meat quality than in homozygotes. The obesity gene did not influence any trait in the expected progeny difference (EPD) study.