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Abstract Producers have been adopting low crude protein or low SID Lys nursery diets to address enteric health concerns. Therefore, we evaluated the longitudinal impact of these strategies on lifetime pig performance. Weaned mixed sex pigs n = 588; initial body weight (BW) = 6.81 ± 1.34 kg] sourced from a poor enteric health flow, were randomly assigned to pens and to one of four nursery dietary treatments, fed for 7 wk. Following the nursery period, pens were then assigned to one of two grow-finish treatments, fed until marketing, to complete a 2 × 2 × 2 factorial design (n = 6 pens/treatment, 12 to 13 pigs/pen). Phase 1 nursery diets were formulated to a 1.10% or 1.40% SID Lys (nLLys or nHLys) with amino acids (AA) provided by both soybean meal (SBM) and crystalline AA or SBM only (nLSBM or nHSBM, respectively). Nursery phase 2 and 3 diets were formulated with a 0.05% decrease in SID Lys while maintaining a 0.30% differential between high and low lysine treatments. Following the nursery, grow-finish pigs were fed diets formulated to equal SID Lys:ME with either a conventional crystalline AA (gfLSBM) or high SBM diet lacking crystalline AA (gfHSBM) to meet AA requirements. During the nursery, enteric health was assessed by fecal pathogen PCRs and bacterial culture, confirming a high natural rotavirus and F18 enterotoxigenic Escherichia coli burden. Pig BW and pen feed disappearance were recorded at the beginning and end of each phase to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (gain to feed ratio; G:F). Data were analyzed with pen as the experimental unit and the fixed effects of nursery SID Lys (nLys), nursery SBM (nSBM), grow-finish SBM (gfSBM), and the two- and three-way interactions using ANOVA. There were no three-way interactions for ADG or ADFI on final performance and no two-way interactions of nLys by nSBM in the nursery. Additionally, there was no effect of nSBM on overall nursery ADG, ADFI, and G:F (P 0.05). Pigs fed nHLys-gfHSBM (0.84 kg/d) had improved overall ADG versus pigs fed nLLys-gfHSBM (0.80 kg/d; interaction; P = 0.010). Final nursery ADG (0.47 vs. 0.42 kg/d), G:F (0.70 vs. 0.63), and ending BW (30.9 vs. 28.0 kg) were greater in pens fed nHLys compared with nLLys (P 0.001). Grow-finish pigs fed gfHSBM were more efficient compared with gfLSBM overall (0.457 vs. 0.449, respectively; P = 0.016). Although pigs fed nHLys had improved ending ADG compared with nLLys (0.83 vs. 0.81 kg/d; P = 0.018, respectively), there were no differences in final BW (128.0 vs. 127.0 kg) or ADFI (1.83 vs. 1.80 kg/d; P 0.05). In conclusion, low SID Lys enteric diets did not improve wean-to-market pig performance in enterically challenged pigs and there was no difference between amino acid sources (crystalline vs SBM).
Miller et al. (Wed,) studied this question.