A group of European researchers recently published a comprehensive study on correlating chemical composition of soybean meal to ileal digestibilities of amino acids and protein in broilers. In this study 22 soybean meal (SBM) samples were collected at the Hamburg, Germany port from three countries (USA (8), Brazil (7) and Argentina (7)). The SBM lots were analyzed for chemical composition and the coefficient of standardized ideal digestibilities were determined in 21-day old broilers chicks (Ross 308). The chicks were fed a commercial corn-SBM diet from 1-17 days and then fed an experimental diet where SBM was included in the diet as the sole source of protein (20.5% crude protein) for three days. Feed, meal and ideal digesta samples were collected and analyzed using standard methods.
The research team used the analytical data to develop prediction equations for the coefficient of standard ideal digestibility of crude protein and lysine based on chemical analyses of these 22 SBMs. The formula for estimating coefficient of standard ileal digestibility of SBM’s crude protein was determined to be: (75.5 + 0.161 KOH solubility) which had an R² of 0.485). Adding crude protein and reactive lysine to the formula resulted in the following formula (29.3 + 0.123 KOH solubility + 0.284 crude proteins + 0.395 reactive lysine) and improved the R² to 0.713).
Whereas, the formula for estimating coefficient of standard ileal digestibility of SBM’s lysine was determined to be: (71.6 + 0.118 KOH solubility + 0.190 crude protein). This formula has a R² of 0.459. Both formulas provide reasonable accurate estimates for standard ileal digestibility values for crude protein and lysine in soybean meals.
The research group concluded that the commercial SBMs tested differed widely in nutrient content, crude protein quality and ideal digestibilities of most amino acids. The coefficients of standard ileal digestibilities of crude protein and lysine of the SBM were positively correlated with crude protein content, KOL solubility, trypsin inhibitor activity and reactive lysine, whereas non-detergent fiber and the oligosaccharides did not seem correlated. The coefficient of standard ileal digestibilities for lysine and most other amino acids in the US and Brazilian SBMs were higher than those for the Argentine meals. KOH solubility was the best predictor of the digestibility of both crude protein and lysine. The article’s authors suggested that using a combination of ileal digestibility values determined using chicks and analytical values may allow the nutritionist to better evaluate commercial SBMs and formulate diets that support greater performance.