Genetic parameters for intramuscular fatty acid composition and metabolism in pigs.

The aim of this study was to estimate genetic parameters for pork intramuscular fatty acid (FA) composition and indices for desaturase and elongase activities involved in n-3 and n-6 PUFA metabolism. The LM of 437 slaughter pigs was analyzed for FA composition (expressed as g/100 g of FA). Indices for enzyme activities were calculated from product to precursor FA ratios. Genetic parameters were estimated with single- and multi-trait animal models. The total FA content, reflecting the intramuscular fat content, was either included or not in the model. Results from the models without total FA content showed relatively high heritability estimates, generally above 0.50, for the proportion of the most important MUFA and PUFA, compared with much smaller values for the SFA. When total FA content was included in the models, heritability values decreased (P < 0.001) for most individual FA and for all sums of FA groups, except for C18:0, C18:3n-6, and C18:3n-3. Heritability estimates for the ratios C20:4n-6/C18:2n-6 and C22:6n-3/C18:3n-3, reflecting the overall conversion in the n-6 and n-3 PUFA pathway, respectively, were 0.29 and 0.35, respectively, with total FA content in the model and increased to 0.38 and 0.49, respectively, if total FA content was not in the model. Heritabilities for other more specific indices were of the same order. Genetic correlations between PUFA proportions and indices for enzyme activities with ADG were mostly negative, whereas the correlations with carcass lean meat percentage were mostly positive. It was concluded that there is meaningful genetic variation for long-chain PUFA metabolism that is only partly dependent on the carcass and muscle fat content. This may allow selection for improved FA composition of pork.