Feeding a Diet with a Near Optimal Amino Acid Profile Improves Energy Utilization for Milk Production in Lactating Sows

The goal of the study was to test the hypothesis that feeding a diet containing near optimal AA profile to lactating sows increases ME utilization efficiency for milk production. Thirty-nine lactating multiparous sows were allotted to 1 of 3 diets: Control 19.60% CP (CON), near ideal AA profile 14.22% CP + crystalline AA (OPT) and as OPT + Leu to create an imbalanced profile. Energy balances (EB) were conducted early lactation (EL, d 4-7) and peak lactation (PL, d 14-17). In EL, compared to Control, EB did not differ for sows fed OPT and was lower (P < 0.05) for sows fed OPTLEU. Compared to OPT, EB of sows fed OPTLEU did not differ. Compared to Control, maternal energy retention did not differ in sows fed OPT and OPTLEU and between sows fed OPT and OPTLEU. Milk energy output (Mcal/d) did not differ between Control (9.83 ± 0.91), OPT (10.73 ± 0.91) and OPTLEU (10.53 ± 0.91). In PL, EB did not differ between OPT and Control, and was lower (P < 0.01) for sows fed OPTLEU compared to Control and OPT. Compared to Control, maternal energy retention was lower (P < 0.01) in OPT and OPTLEU. Milk energy output (Mcal/d), compared to Control (12.37 ± 0.89) was greater (P < 0.01) in sows fed OPT (16.65 ± 0.89) and did not differ in sows fed OPTLEU (13.82 ± 0.89). Compared to OPT, milk energy output was lower (P < 0.05) for sows fed OPTLEU. In EL compared to Control, energy efficiency (EE) did not differ in OPT and OPTLEU, and were 71, 83 and 79 % ± 5, respectively. In PL compared to Control, EE was greater (P < 0.05) in OPT and did not differ for OPTLEU, and were 66, 83, and 73% ± 5, respectively. Heat production (HP) associated with milk yield did not differ between Control, OPT and OPTLEU in EL and were 65.3, 42.2 and 43.9 ± 18.5 kcal/(d·BW^0.75), respectively. In PL, compared to Control, HP tended to be lower (P = 0.081) in OPT and did not differ for OPTLEU, with HP values of 107.8, 63.3 and 93.9 ± 17.1 kcal/(d·BW^0.75). Sows fed a diet with near ideal AA profile have greater energy partitioning to milk production and have higher EE utilization for milk. Adding Leu to create an imbalance reduced the EE utilization and partitioning of energy to milk.