ISSUE FOCUS 40 FEED & ADDITIVE MAGAZINE April 2025 treatments in a randomized complete block design with 20 pens per treatment. Soybean meal NE value used in diet formulation was 2,087 kcal/kg (78% NE of corn; NRC, 2012). The four treatments consisted of a diet containing a low level of SBM and added feed-grade amino acids (Low SBM) and three diets with 3.37 (Med-Low SBM), 6.69 (Med-High SBM), and 10% (High SBM) increase in SBM level compared to the Low SBM diet and decreased added feed-grade amino acids. The High SBM diet did not contain feed-grade L-lysine. Treatment diets were fed in four phases. Phase 1 and 4 diets are shown in tables 1 and 2, respectively. Pigs were weighed and feed disappearance was measured every 14 d to determine ADG, ADFI, and F/G. Caloric efficiency (CE) was determined on an NE basis and was calculated by multiplying total feed intake, kg × energy content of the diet (kcal/kg) and dividing by total kg of gain. Three weeks prior to the end of the study, the 4 heaviest pigs in each pen were selected and marketed. The remaining pigs at the end of the study were tattooed with the specific pen identification number and marketed at a commercial abattoir (JBS Swift, Worthington, MN) for collection of carcass yield (carcass/live weight), BF, loin depth (LD), percentage lean, and hot carcass weight (HCW) for each individual carcass. Experimental data were analyzed using the lmer function in R Studio (Version 4.2.2, R Core Team, Vienna, Austria) with pen serving as the experimental unit in a randomized complete block design within each of the two experimental barns. For all data, treatment served as a fixed effect within the statistical model, with the cross product of barn and block serving as a random effect. For carcass characteristics, pen was included as a random effect, and HCW was used as a covariate for all responses other than itself. Fixed effects were tested using the joint tests function in R, and treatment means were estimated using the emmeans function. Linear and quadratic contrasts were constructed with decreasing levels of SBM. Total removals and mortality data were analyzed assuming a binomial distribution with a logit link function. Results were considered significant at P ≤ 0.05 and marginally significant at P ≤ 0.10. RESULTS Live performance data summarized by day 0 to 56, day 56 to 112 and over the entire trial (0 to 112) are shown in table 3 along with mortality, removals and carcass characteristics. Increasing the level of SBM and decreasing dietary FGAA linearly (P<0.004) decreased BW at both day 56 and 112. Hence, ADG was linearly (P<0.001) increased with increasing dietary levels of FGAA with decreasing SBM from day 0 to 56 and over the trial period (day 0 to 112), but only a tendancy for linear (P<.10) improvement was observed from day 56 to 112 interval. A linear (P<.004) increase in ADFI was observed in the day 0 to 56 period and over entire 112-day trial period with increasing dietary levels of FGAA, but not during the day 56 to 112 interval. A significant linear (P<.05) improvement for FCR was observed for increasing dietary levels of FGAA in the day 56 to 112 period, but not from day 0 to 56 or over the trial period. CE was calculated for each diet using individual ingredient NE estimates from NRC (2012) then by
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