Effects of feeding levels on ileal amino acid digestibility of extruded full fat soybeans in nongestating sows

Abstract The objectives of this study were to investigate the effect of feeding levels on amino acid (AA) digestibility of extruded full fat soybeans (EFSB) fed to nongestating sows and to provide a reference for setting feed intake level when evaluating the quality of nutrients in the feed ingested by sows. Twelve nongestating sows (parity 3 to 5) were fitted with a T-cannula at the distal ileum. After recovery, sows were assigned to a replicated 6 × 3 incomplete Latin square design using two diets (nitrogen-free and EFSB) and three levels of feed intake (1.3, 2.0, and 3.4 times the maintenance requirement for metabolizable energy (ME)). The design included six dietary treatments and three periods, and each period contained two replicates for a total of six replicate sows per treatment. All diets contained 0.3% chromic oxide as an indigestible marker. In each period, ileal digesta samples were collected continuously for 12 h on days 6 and 7 after 5 d of acclimation to the experimental diet. Results of the experiment indicated that different feeding levels (1.3, 2.0, and 3.4 times the maintenance requirement for ME) had no effects on apparent ileal digestibility (AID) of AA and standardized ileal digestibility (SID) of AA, but feeding level did affect the endogenous AA loss estimated using the nitrogen-free diet method. Endogenous phenylalanine excretion was greater with 1.3 times than with 3.4 times the maintenance requirement for ME (P = 0.03), and endogenous tyrosine excretion was greater with 1.3 and 2.0 times than with 3.4 times the maintenance requirement for ME (P = 0.01). Increasing feed consumption resulted in greater loss of total endogenous AAs and crude protein (CP). In conclusion, feeding levels of 1.3 to 3.4 times the maintenance requirement for ME did not affect the AID and SID of AA of EFSB fed to nongestating sows.