Recovery of amino acids at the distal ileum for determining apparent and true ileal amino acid digestibilities in growing pigs fed various heat-processed full-fat soybean products.

Ten crossbred gilts fitted with simple T-cannulas at the distal ileum were used to determine the apparent and true ileal amino acid digestibilities in five different soybean products: extruded, jetsploded, micronized, or roasted full-fat soybeans (FFSB) and soybean meal (SBM). The gilts with an average initial body weight of 36 kg were fed the different diets according to a replicated 5 x 5 Latin square design. Gilts were fed twice daily at 0800 and 1830 at 2.6 times maintenance energy requirement. All diets were cornstarch-based and formulated to contain 16% CP from one of the five soybean products. The recovery of endogenous lysine at the distal ileum was determined using the homoarginine technique. This technique involved the guanidination of dietary lysine to homoarginine, to allow for a differentiation between undigested dietary lysine, represented by homoarginine, and endogenous lysine in the digestive tract of pigs consuming diets that contain guanidinated proteins. Chromic oxide and dysprosium chloride were included as indigestible markers in the normal and homoarginine diets, respectively. True digestibilities were only determined with the five gilts of one Latin square. Ileal digesta were collected for 24 h on d 8 and 10 of each 10-d experimental period. The apparent ileal protein digestibility was higher in SBM than in other soybean products (P < .05). In the heat-treated FFSB, the apparent protein digestibility varied between 69.0 and 81.6%. Recovery of endogenous lysine was affected by the diet (P < .01) and varied between 1,329 and 2,448 mg/kg of DM intake.(ABSTRACT TRUNCATED AT 250 WORDS)