Production of crystalline l-Thr results in the generation of a Thr biomass that contains more than 80% CP, 5.20% Lys, 5.10% Val, 4.52% Thr, 4.15% Ile, and 1.06% Trp. This Thr biomass product can possibly be used as a feed ingredient in diets fed to weanling pigs, but there is little information about the nutritional value of this product. The objective of this work was to determine the AA digestibility and energy concentration in Thr biomass and to compare these values to values obtained for fish meal in diets fed to pigs. The apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of CP and AA were determined in Exp. 1. Nine pigs (initial BW: 13.4 ± 2.5 kg) were equipped with a T-cannula in the distal ileum and allotted to a triplicated 3 × 3 Latin square design with 3 diets and 3 periods in each square. One diet contained 20.0% Thr biomass as the sole source of AA, and a second diet contained 25.0% fish meal as the sole source of AA. The last diet was a N-free diet that was used to measure basal endogenous losses of AA and CP. Results indicated that the AID and SID of all AA except Trp, Gly, and Pro were greater (P < 0.05) in Thr biomass than in fish meal. In Exp. 2, 24 pigs (initial BW: 18.1 ± 3.5 kg) were placed in metabolism cages and randomly allotted to 3 diets. The first diet contained 96.4% corn, the second diet contained 79.3% corn and 17.0% Thr biomass, and the third diet contained 75.3% corn and 24.0% fish meal. Total collection of feces and urine was performed for 5 d after a 5-d adaptation period, and all samples of ingredients, diets, feces, and urine were analyzed for GE. Digestible energy and ME were then calculated. The DE in the Thr biomass was greater (P < 0.05) than in fish meal and corn (4,935 vs. 3,938 and 3,939 kcal DE/kg DM, respectively), and the ME in the Thr biomass was also greater (P < 0.05) than in fish meal and corn (4,335 vs. 3,508 and 3,839 kcal ME/kg DM, respectively). Results from these experiments indicate that Thr biomass is an excellent source of AA and ME. Therefore, the Thr biomass is a viable ingredient that can be used as an alternative to fish meal and possibly other animal proteins in diets for pigs.
Keywords: amino acids; digestibility; energy; fish meal; pig; threonine biomass.