PSV-12 - Evaluation of dietary crude protein and acid-binding capacity on nursery pig growth performance and fecal dry matter

Abstract: A 42-d study used 360 pigs (241 × 600 DNA; initially 5.2 ± 0.01 kg) to assess the effects of dietary crude protein (CP) and acid-binding capacity at a pH of 4 (ABC-4) on growth performance and fecal dry matter (DM). Pens were randomly allotted to 1 of 6 treatments in a generalized randomized block design with 5 pigs/pen and 12 pens/treatment. Diets were corn-soybean meal-based, arranged in a 2×2+2 factorial. The first factor, ABC-4, involved manipulating dietary acid binding capacity by substituting whey powder and permeate for lactose, HP 300 for AX3, and using fumaric/formic acid to achieve 200 meq/kg and 250 meq/kg in phases 1 and 2, respectively, compared to a traditional formulation (TF) where ABC-4 level was uncontrolled. The second factor, CP, was tested at 21% and 18%, with a consistent SID Lys:CP ratio of approximately 6.40. The 6 treatments included: 1) low ABC-4 at 21% CP, 2) low ABC-4 at 18% CP, 3) TF at 21% CP, 4) TF at 18% CP, 5) treatment 3 with 3,000 mg/kg zinc oxide (phase 1) and 2,000 mg/kg (phase 2), and 6) treatment 4 with additional amino acids (AA) to achieve the same levels of Lys, Met, Thr, Trp, Val, and Ile as the 21% CP diet. Treatments were fed for phase 1 (d 0 to 7) and phase 2 (d 7 to 21) with a common diet for phase 3 (d 21 to 42). From d 0 to 21, an ABC-4 × CP interaction was observed (P = 0.021), where diets at 21% CP improved G:F (P < 0.001) over diets with 18% CP, with a greater response in the low ABC-4 diets. An increase in ADG, ADFI, and G:F was observed (P ≤ 0.035) when ZnO was added to the traditional 21% CP diet. Also, G:F increased (P < 0.001) with additional feed-grade AA in the traditional 18% CP diet. For fecal DM, an ABC-4 × CP × day interaction was observed (P = 0.043). Low ABC-4 diets increased fecal DM on both d 7 and 21 compared to traditional diets; however, decreasing CP only increased fecal DM on d 7 in traditional diets and d 21 in low ABC-4 diets. On d 7, pigs fed the 21% CP + ZnO and 18% CP + AA treatments both had higher (P ≤ 0.027) fecal DM compared to their respective treatments of comparison, with no differences on d 21. In summary, formulating diets with a low ABC-4 approach improved both G:F and fecal DM in nursery pigs. Reducing CP to 18% worsened growth performance compared to 21% CP, but adding additional AA partially returned performance to levels achieved by pigs fed 21% CP diets, while improving fecal DM.