EFFECT OF DIETARY LARD ON PERFORMANCE, FATTY-ACID COMPOSITION AND SUSCEPTIBILITY TO LIPID-PEROXIDATION IN GROWING-FINISHING FEMALE AND ENTIRE MALE PIGS

The effect of increasing the energy concentration of growing-finishing pig diets through inclusion of lard on performance, carcass and meat composition and lipid susceptibility to peroxidation was studied. A to tal of 720 Landrace x Large White male and female pigs (equal number o f entire males and females) were used. Experimental diets were formula ted to have a low (3000 kcal ME kg(-1)) or high (3200 kcal ME kg(-1)) energy level, but in all cases to have a constant lysine:ME ratio. Thi s was achieved using a low (6.8 g kg(-1)) and a high (49.3 g kg(-1)) l evel of dietary lard inclusion. Gilts had lower daily gain (P < 0.0001 ) and worse feed conversion efficiency (P < 0.0001) than entire males. Susceptibility to oxidation was not affected by sex. Fat concentratio n in pig diets equilibrated in metabolizable energy and protein did no t modify average gain, but reduced feed intake (P < 0.02), improved th e gain:feed ratio (P < 0.0001), increased dressing percentage (P < 0.0 2) and produced higher carcass weight (P < 0.01). Carcass backfat and lean percentage were not affected by dietary treatment. A reduction in the proportion of(n-3) fatty acids in phospholipids (P < 0.03), a hig her (n-6):(n-3) ratio (P < 0.01) and a lower susceptibility of muscle homogenates to oxidation was found in animals receiving higher levels of dietary lard (P < 0.01).