This paper provides credible net energy (NE) estimates for soybean meal (SBM) based on recent indirect calorimetry (IC) and growth assay procedures. The latter was in remarkable agreement (<1.0% difference) with the calorimetric gold standard; both exceeding calculated estimates reported from international composition tables by 8-15%. The empirical studies were conducted in academic facilities with strict environmental control. This setting lacks pathogen induced immune stress that would increase maintenance energy use for protective functions and bias the NE estimate. The growth assay was then used to determine the veracity of the SBM NE estimate in the commercial environment, with the expectation of a similar value. However, this yielded an estimate of 3302 kcal NE/kg SBM dry matter (DM), which exceeded our previous growth assay estimate from an academic equivalent setting (2492) by 32%. This increase in ‘apparent SBM NE’ (est. +810 kcal/kg DM) does not represent a difference in classic NE estimates. We assert that the IC estimate for SBM NE (2517) represents that because it is based on SBM substrate energetics. However, applying the growth assay in the commercial setting was the means of detecting a role for SBM that we had not anticipated. SBM appeared to cause greater total diet NE use for growth since caloric efficiency improved with increasing SBM level; SBM NE being fixed. Since SBM NE was known, we proposed that the apparent SBM ‘NE’ value in the commercial setting is the sum of (1) classic ingredient energetics, and (2) conservation of total dietary energy for growth; SBM mediating an ‘uplift’ in diet NE for growth. The abundance of health-promoting compounds in SBM may have prevented diversion of energy from growth to expand protective functions to combat environmental stress (e.g. pathogen-induced immunity). We describe this combination of NE provision and diet NE conservation as Productive energy (PE). Our observations are aligned with subsequent research results by commercial systems. Consequently, practicing nutritionists are increasingly applying SBM PE values when formulating diets for commercial conditions.
Boyd, R. and A. Gaines. 2024. Soybean Meal Net Energy Value for Growing Pigs is Greater in Commercial Environments: How Can This Be? 23rd Annual Midwest Swine Nutrition Conference Proceedings, pp. 37-44.