Apparent and standardized ileal digestibility of amino acids in gelatin-based diets by growing pigs

A study was conducted with the objectives of measuring the coefficients of ileal apparent digestibility (CIAD) and coefficients of ileal standardized digestibility (CISD) of amino acids (AA) in two gelatin-based diets and in soybean meal by growing pigs. Four individually housed pigs (initial BW: 44.1 ± 1.45 kg) were equipped with T-cannulas in the distal ileum. Two diets based on gelatin of either pork or beef origin were formulated using mainly corn starch, sucrose, and gelatin. These diets were fortified with l-histidine, l-isoleucine, dl-methionine, and l-tryptophan. Two additional diets were formulated: one included soybean meal as the only AA-containing ingredient, and the other was a nitrogen-free (N-free) diet. The N-free diet was used to estimate the basal endogenous losses of crude protein (CP) and AA by the pigs. Chromic oxide (4 g/kg) was included in all diets as an indigestible marker. Each of the four diets was fed to each of the four pigs during a 7-day period with digesta being collected in 10 h periods on day-6 and day-7. The CIAD and CISD of CP and AA in the two gelatin-based diets were compared to the CIAD and CISD in soybean meal. Results of the experiment showed that there was no difference (P > 0.05) in CIAD and CISD for any of the indispensable AA between the pork gelatin-based diet and soybean meal. The beef gelatin-based diet had a lower CIAD for His and Thr, and a lower CISD for Thr compared to soybean meal (P < 0.05), but no differences (P > 0.05) for the remaining indispensable AA were observed. It is concluded that the AA in both pork and beef gelatin are highly digestible and both these feed ingredients may be used as a protein source in diets for growing pigs provided that crystalline His, Ile, Met and Trp are added to balance the indispensable AA.