Between and within breed variation for lean growth and intramuscular fat content and fatty acid composition in pigs

A first experiment in 229 barrows examined the effect of the genetic type on growth, carcass composition and intramuscular fat (IMF) content and composition. Four genetic types were used: Landrace x Large White (LSLW), Duroc, either inseminated with boars from the same (D1D1) or a different line (D1D2), and Duroc x Iberian (D1IB). All pigs were reared until 200 days under the same conditions. IMF was analysed in the gluteus medius muscle. The LSLW barrows grew faster than the other types. IMF displayed an inverse relationship with carcass lean content, with values being 5.6, 4.4, 3.4, and 1.9% for D1IB, D1D1, D1D2, and LSLW, respectively. The most saturated IMF was observed in D1IB whereas the most polyunsaturated in LSLW. Purebred D1D1 showed a higher proportion of monounsaturated fatty acids than D1D2, where IMF was instead more polyunsaturated. A second experiment has been initiated in D1 to test whether selection against backfat depth at restrained body weight and IMF content is a useful strategy for reducing backfat but not IMF. Preliminary results at hand indicate that selected pigs (n=106) showed lower backfat depth than controls (n=110), with no significant change in IMF content and composition.