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 digestib ilities in five different soybean products: extruded, jetsploded, micr onized, or roasted full-fat soybeans (FFSB) and soybean meal(SBM). The gilts with an average initial body weight of 36 kg were fed the diffe rent 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 endogen ous lysine at the distal ileum was determined using the homoarginine t echnique. This technique involved the guanidination of dietary lysine to homoarginine, to allow for a differentiation between undigested die tary lysine, represented by homoarginine, and endogenous lysine in the digestive tract of pigs consuming diets that contain guanidinated pro teins. Chromic oxide and dysprosium chloride were included as indigest ible 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 h igher in SBM than in other soybean products (P <.05). In the heat-trea ted FFSB, the apparent protein digestibility varied between 69.0 and 8 1.6%. Recovery of endogenous lysine was affected by the diet (P <.01) and varied between 1,329 and 2,448 mg/kg of DM intake. True lysine dig estibility was higher in SBM(P<.05) than in roasted or jet-sploded FFS B; extruded and micronized FFSB were intermediate. With the exclusion of extruded FFSB, protein nitrogen flows were higher when FFSB were fe d than when SBM was fed (P <.05). Free amino acid nitrogen flows expre ssed as a percentage of total amino acid nitrogen flow were not influe nced by treatment (P >.05).