Association of fatty acid synthase gene and malic enzyme gene polymorphisms with fatness in turkeys.

A candidate gene approach was carried out on a commercial line of turkeys to assess the association between fatness variability and polymorphisms of genes involved in lipid metabolism. Four restriction fragment length polymorphisms (RFLP) were typed on the fatty acid synthase gene (MspI/pF5), on the malic enzyme gene (HindIII/em), as well as on the acetyl coenzyme A carboxylase and delta9 desaturase genes. Fatness level was estimated in vivo by an ultrasonic instrument. Fat yield was assessed after slaughter by calculating the ratio of the leg skin plus subcutaneous fat weight to the whole leg weight. Finally, the lipid content was determined by extraction from the boneless leg. The 84 female turkeys sampled were full and half-sibs born from eight sires, seven of which were heterozygous for MspI/pF5 or HindIII/em RFLP and one of which was double homozygous at these loci. The analyses of variance used to compare the genotypes at each RFLP suggested a major role associated with the fatty acid synthase gene polymorphism in the explanation of fatness variability. One homozygous genotype for MspI/pF5 was about 1.5 standard deviations leaner than the other two homozygous genotypes. An analysis of the average effects of gene substitution confirmed the association between leanness and one allele of the fatty acid synthase polymorphism. It also identified a significant association between leanness and one malic enzyme RFLP allele, congruent with a strictly additive determinism for the effect associated with this polymorphism. This experiment provided new evidence of the association between both fatty acid synthase and malic enzyme gene polymorphisms and fatness variability in turkeys.

DNA polymorphisms of lipogenesis genes and analysis of linkage with fatness in turkeys.

DNA variability of lipogenesis genes was evaluated by Restriction Fragment Length Polymorphism (RFLP) on four selected lines of turkeys. Thirteen polymorphisms were obtained, four on the acetyl-coenzyme A carboxylase gene, one on the apoprotein AI gene, two on the malic enzyme gene, four on the fatty acid synthase gene, and two on the stearoyl-coenzyme A mesaturase gene. Six of these RFLP were studied in more detail on 64 female turkeys sampled in two lines. Large differences in terms of number of DNA profiles and haplotype frequencies were observed between the two genes, in accordance with the variability of recorded fatness performances. An additive model including the effects of RFLP profiles was used to assess linkage between polymorphisms on lipogenesis genes and fatness measured either in vivo by an ultrasonic instrument or, after slaughter, by the ratio of skin plus subcutaneous fat weight to the whole leg weight. In each line, two polymorphisms suggested a statistical association with fat deposit, one on the malic enzyme gene detected by DNA digestion with HindIII and one on the fatty acid synthase gene detected by MspI. A multiple comparison of means associated with each RFLP profile enabled the identification of two lean profiles in one strain, and a fat profile in the other.