ISSUE FOCUS 44 FEED & ADDITIVE MAGAZINE April 2025 multiplying total feed intake, kg × NE content of the diet (kcal/kg) and dividing by total kg of gain (live or carcass). As expected, using current NRC (2012) SBM NE estimates (2,087 kcal/kg), CE on a live weight basis was linearly (P<0.003) improved with increasing SBM, but not on a carcass basis (P=.146) due to decreased carcass weight observed with increasing levels of dietary SBM. Since FCR over the entire feeding period was not impacted (P=.246), an estimate of the NE of SBM was calculated by adjusting NE of SBM used in formulation (thus changing dietary NE) until CE for all treatments were equal. Estimated NE value of SBM was 93.5% on a liveweight basis and 83.9% on a carcass weight basis relative to the NE of corn based on this study results. Carcass weight, yield percentage and ADG were linearly (P<0.001) increased with decreasing levels of SBM and consequential increase in dietary FGAA. Carcass FCR was also linearly (P<0.02) improved with increasing levels of FGAA. BF (P<.10) carcass lean percentage (P<.05) increased in a quadratic manner (P<.10) with increasing FGAA. Interestingly, removals from treatment were linearly (P<.03) increased with increasing dietary levels of SBM. While mortality was unaffected (P>.41), however the combined removals and mortality percentage linearly (P<.01) increased with increasing levels of dietary SBM. DISCUSSION The current trial clearly demonstrates the live performance and carcass benefits of using FGAA instead of a corn-SBM only diet for growing finishing pigs. These findings contrast with Cemin, et al. (2020) and Holen et al. (2022) who reported lower live performance with increasing FGAA with decreasing dietary SBM levels, though both sets of authors indicated formulating to NRC (2012) amino acid recommendations. However, there were no dietary adjustment or acknowledgment for phenylalanine, tyrosine or Arg levels. In a CJ sponsored trial (Williams et al. 2021) evaluating high FGAA levels in late nursery and early grower pigs, we observed equal BW and ADG when increasing dietary FGAA but could not maintain FCR. We speculate the increased ADFI observed with increasing FGAA was due to a co-limiting amino acid or nitrogen deficiency. This theory could help explain the lower performance observed by Cemin et al. (2020) and Holen et al. (2022) as the linear depression in growth in both experiments were primarily driven by the poor performance on the diets with the lowest level of SBM and highest level of FGAA. Cemin et al. (2020) concluded “Using CE to estimate the energy of SBM relative to corn, a value of 105.4% of corn energy or 2816 kcal/kg NE was determined using all data points. When removing the CE value of the 39% SBM treatment due to the quadratic tendency, SBM was estimated to have 121.1% of corn energy or 3236 kcal/kg NE.” The authors attributed all the differences in growth and efficiency on the NE of SBM, not accounting for any other variables such potential amino acid deficiency. CE is a calculation of calculations, hence if any one of the assumptions are incorrect then the final calculation is incorrect. The NE of SBM is likely higher than the NRC estimate of 2,087 kcal/kg. However, when evaluating net energy of SBM from biochemical and physiological approach, one cannot conclude SBM has equal or higher NE than corn. Recently Dr. Stein’s lab has employed the use of group housed indirect calorimetry to determine NE content of various feed ingredients. Stein (2024) reported on a trial evaluating the NE of US soybean meal and concluded a value of 2233 kcal/kg. This result is 83.6% of NRC (2012). This estimate of corn NE is very close to the calculated 83.9% relative to corn we observed on a carcass basis in the present study. The use of FGAA is an important tool to lower feed cost while lowering nitrogen emission for swine and poultry producers. When FGAA’s are used within the known limits, they can improve animal performance and enhance carcass value. However, when lowering dietary crude protein via SBM or other protein sources, care must be taken as all the
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