Prediction of standardized heal digestibility and essential amino acid content of ingredients in swine: A meta-analysis

Amino acid (AA) composition and digestibility are major determinants of nutritional value. These factors vary considerably in animal feed ingredients. For pig feed ingredients, standardized ileal digestibility (SID) is commonly used as an estimate of nutritional AA value. In this study, relationships between ingredient proximate composition and AA content, AA content and essential AA apparent heal digestibility (AID), and between SID and AID were characterized using databases compiled from published research. The effects of ingredients (cereals, cereal by-products, oilseeds, legume seeds and oilseed meals), surgical procedure (T-cannula, re-entrant cannulas, post-valve T-cannulas and ileorectal anastomy) and animal weight (<= or >25 kg) were modelled. Relationships between independent variables were examined for each AA to avoid co-linearity. The best predictor of AA content was crude protein (significant slope, P< 0.001, high R-2, low error) for all ingredients except for faba bean (R-2 = 0.143-0.805). For dietary lysine, prediction accuracy was best for peas, lupin and barley, with root mean square errors prediction of 3.84%, 8.08% and 1.89% respectively. Neither ingredients nor surgical procedure (P>0.1) nor the basal endogenous nitrogen loss estimation method (P>0.1) appeared to affect the accuracy of essential AA (EM) AID estimation from tEAA and EM SID estimation from AID. Apparent ileal digestibility was the best predictor of essential EAA SID (R-2 = 0.911-0.987), slope near unity and a significant intercept representing basal endogenous nitrogen loss). Compared to published models, the studied models had improved R-2 and offered better accuracy. (C) 2015 Elsevier B.V. All rights reserved.