Standardized Ileal Digestibility of Amino Acids in L-Amino Acids Sources and Single Cell Protein Biomass Coproduct for Pigs.

Nine male pigs, which average 44.8 ± 3.6 kg body weight, were surgically fitted with a T cannula in the terminal ileum of the small intestine. The animals were assigned to a triplicated 3 × 2 incomplete Latin square design, consisting of three treatments: a complete mixture of industrial amino acids (L-AAs), a single cell protein (SCP) biomass coproduct, and an nitrogen-free diet. The animals were fed twice a day, with 5 days of adaptation to the experimental diets, followed by 2 days of continuous collection of ileal digesta for 10 h. Titanium dioxide was included in all diets at 0.5% as an indigestibility marker, and the N-free diet was used to estimate basal endogenous ileal losses of amino acids (AA). The standardized ileal digestibility (SID) of crude protein was higher (p < 0.05) for L-AAs compared to SCP (101.3% vs. 73.4%). For the indispensable and dispensable AA, the L-AAs also presented higher SID (p < 0.05) to SCP. Specifically for L-tryptophan, the SID of SCP was 89.2%. These results highlight that L-AAs are highly digestible, with SID values close to 100%, whereas SCP demonstrates viability as a source of indispensable and dispensable AA in swine nutrition.