Feeding a Diet with a Near Ideal Amino Acid Profile Improves Amino Acid Utilization Efficiency for Milk Production in Sows

The study was conducted to test the hypothesis that improving dietary AA balance increases essential AA (EAA) efficiency for milk production. Fifty-four lactating multiparous Yorkshire sows were allocated to 1 of 3 diets: 19.60% CP (control) with no crystalline AA (CAA), an improved AA balance diet (BAL) containing 14.22% CP and CAA (l-Lys, dl- l-Met, l-Thr, l-Trp, l-Val, l-Ile, l-Phe, l-His) and an imbalanced AA diet (IMB) containing 14.56% CP and CAA as BAL + 0.45% l-Leu. All diets contained the same SID Lys (0.9%) and NE (2,580 kcal/kg). Sow body weight and backfat were recorded on d 1 and 21 to estimate body protein mobilization (BPM). Piglet BW was recorded on d 4, 8, 14 and 18 to estimate milk yield in early lactation (EL; d 4-8) and peak lactation (PL; d 14-18). Amino acids efficiencies were calculated based on milk AA output relative to SID AA intake corrected for AA contribution from BPM. Model included sow as random, and diet, replicate, parity, lactation stage (EL and PL) as fixed effects. In EL, compared to Control, BAL had greater (P < 0.05) efficiencies of Arg, His, Ile, Leu, Phe and Trp (51, 70, 63, 64, 49 and 88% vs. 30, 52, 43, 43, 37 and 62%, respectively). Efficiencies of Lys, Met, Thr and Val did not differ between BAL and Control (61, 58, 60 and 51% vs. 60, 65, 56 and 51%, respectively). Compared with BAL, IMB efficiency of Leu was lower (43.3% vs. 64.2%, P < 0.01), and that of Arg, His, Ile, Lys, Met, Phe, Thr, Trp, and Val did not differ (52, 69, 62, 60, 57, 48, 59, 85 and 50%, respectively). In PL, compared to Control, BAL had greater (P < 0.05) efficiencies of Arg, His, Ile, Leu, Lys, Phe, Thr, and Val (70, 94, 84, 86, 82, 65, 80, and 68% vs. 34, 58, 48, 48, 67, 42, 62, 68 and 57%, respectively) except for Met which did not differ (77% vs. 72%). Compared with BAL, IMB had lower (P < 0.05) efficiencies of Arg, His, Ile, Leu, Lys, Met, Phe, Thr and Val (61, 82, 73, 51, 71, 67, 57, 70 and 59%). In PL, improving dietary AA balance increases efficiency of EAA, except Met, for milk production and creating a dietary AA imbalance through dietary supplementation of crystalline l-Leu decreases EAA efficiency for milk production.