Nutritional manipulation increases intramuscular fat levels in the Longissimus muscle of female finisher pigs

Fifty crossbred (Large White x Landrace x Duroc) female finisher pigs were used to determine the effect of nutritional manipulations on intramuscular fat deposition. The main nutritional treatments were (i) Control (pigs fed a commercial grower diet), (ii) -15% P:DE (pigs fed a 15% reduced protein:digestible energy diet during the grower phase), (iii) -30% P:DE (pigs fed a 30% reduced P:DE diet during the grower phase), (iv) +6% Fat (pigs fed diet supplemented with 6% additional fat during the grower phase), and (v) -Vit A (pigs fed a control diet with no supplemented Vit A in the mineral vitamin premix during the grower and finisher phase). Pigs fed the 30% reduced P:DE diet had an inferior feed to liveweight gain (feed conversion ratio, FCR) for the combined grower and finisher growth period (P = 0.036) compared with the other dietary treatments. There were no significant differences in average daily gain (ADG) or voluntary feed intake (VFI) for the grower, finisher, and the combined grower and finisher phases, or liveweight at slaughter between the dietary treatments. Pigs fed the 15% (1.9%) and 30% (2.7%) reduced P:DE diet, and the Vit A-restricted diet (2.0%), had significantly higher intramuscular fat (IMF) levels compared with pigs fed the other diets. Pigs fed the control diet had higher (P = 0.002) carcass dressing percentage compared with pigs fed the other diets. There were no significant dietary effects on total fat tissue (P = 0.661), total lean muscle tissue (P = 0.637), and total bone mineral (P = 0.367) content. In conclusion, these data indicate that feeding pigs grower diets with 15% and 30% reduced P:DE, and grower and finisher diets restricted in Vit A, improved the IMF levels in the Longissimus muscle. The increase in IMF levels in pigs fed the 15% reduced P:DE diet, and grower and finisher diets restricted in Vit A, improved the IMF levels without having a detrimental effect on growth performance and carcass quality