PSIII-13 - Evaluation of reduced dietary crude protein and amino acid concentrations in diets for nursery pigs

Abstract: Reducing crude protein (CP) in diets for nursery pigs exposed to enteric challenges has been suggested to decrease pathogenic bacterial proliferation, diarrhea, morbidity, and mortality. This study evaluated the effects of feeding reduced CP by lowering amino acid (AA) concentrations in the post-weaning diet on growth performance, feed efficiency, and diarrhea incidence in nursery pigs and further evaluated whether increasing amino acid concentrations in the subsequent diet could recover potential lost performance through compensatory growth. Weaned pigs (n=180; 21-day old; BW=6.63±1.32 kg) were randomly assigned within sex and BW blocks to 1 of 4 dietary treatment combinations using 60 pens (3 pigs/pen; 15 replicates/treatment). Treatment combinations consisted of a low or high CP Phase 1 (P1) diet (1.05 and 1.45% standardized ileal digestible (SID) lysine; 17.7 and 22.0% CP, respectively) fed for 2 weeks, and within each, a low or high CP Phase 2 (P2) diet (1.30 and 1.45% SID lysine; 19.9 and 21.9% CP, respectively) fed for 3 weeks. Reductions in CP and SID AA content were made by decreasing dietary soybean meal and crystalline AA. Reducing CP and AA in P1 decreased (P< 0.001) BW (8.60 vs. 9.52 kg), ADG (140.8 vs. 207.1 g/d), ADFI (232.5 vs. 282.0 g/d), and gain:feed (593.4 vs. 730.0 g/kg) at the end of P1. Overall, final BW (20.37 vs. 21.55 kg; P=0.029), ADG (392.5 vs. 426.4 g/d; P=0.026), ADFI (574.3 vs. 610.8 g/d; P=0.008), but not gain:feed (684.5 vs. 704.1; P=0.162), were decreased by low CP and AA in P1, independent of P2 treatment. Increasing CP and AA in P2 decreased ADFI (793.0 vs. 853.1 g/d; P=0.013) and increased gain:feed (707.7 vs. 668.9 g/kg; P=0.003) for P2. Overall, feeding greater CP and AA decreased ADFI (567.3 vs. 617.8 g/d; P=0.008) and increased gain:feed (716.0 vs. 672.5 g/kg; P=0.003) without affecting ADG or final BW, regardless of P1 treatment. Individual pig fecal scores were determined using fecal loops on d 4, 7, 14, 18, and 21 using a scale of 1 to 5 representing hard, normal, soft, watery soft, and watery liquid feces. Scores were collapsed into a dichotomous scale with scores 1-3 representing no diarrhea and scores 4-5 representing diarrhea and analyzed using chi-square analysis. Diarrhea incidence peaked (P< 0.001) on d7 (78.3%) and was lowest on d28 (22.5%). Feeding low CP during P1 reduced the incidence of diarrhea on d14 (P=0.036; 23.9 vs. 31.7%) and the low CP P2 diet reduced diarrhea on d21 (P=0.048; 16.7 vs. 23.9%). In conclusion, incidence of diarrhea was reduced by feeding lower dietary CP concentrations. However, limiting amino acids to reduce CP immediately post-weaning negatively affected growth performance, which could not be recovered by increasing amino acid supply above requirements in the subsequent diet.