Investigating the amino acid digestibility of alternative protein sources and determining the impact of dietary fiber on energy, nitrogen, and amino acid digestibility in growing pigs

Three experiments were designed to quantify the nitrogen (N) and amino acid (AA) digestibility of various protein sources fed to growing pigs. The protein ingredients were sunflower meal, cottonseed meal, canola meal, camelina meal, egg albumen, casein, blood meal, plasma meal, potato protein concentrate, soy protein concentrate, soy protein isolate, and linseed meal, which were fed as the sole source of amino acids for the animals and were included in semi-purified, corn starch-based diets. A semi-purified, nitrogen-free diet (NFD) was used to estimate endogenous losses of AA. In each experiment, pigs were surgically fitted with a simple T-cannula at the distal ileum and fed four experimental diets and the NFD based on a 5 X 2 crossover arrangement in a randomized crossover design, with 5 diets and 2 periods. For experiment 1 (Exp. 1), sunflower meal, cottonseed meal, canola meal, and camelina meal were fed to 19, 42-kg barrows to determine the apparent (AID) and standardized (AID) digestibility of AA at the terminal ileum. The AID and SID of N and all AA were greatest for sunflower meal (P \u3c 0.05), and canola meal had similar AID and SID of N, Met, Thr, Leu, and Val. The AID and SID of all essential AA, except for Met and Trp, was lower in camelina meal than sunflower meal (P \u3c 0.05). Cottonseed meal had lower AID and SID of Lys, Ile, Leu, Met, Thr, and Val compared to the other protein sources (P \u3c 0.05). In experiment 2 (Exp. 2), egg albumen, casein, blood meal, and plasma meal were fed to 20, 20-kg barrows to determine the AID and SID of N and AA. The AID and SID of N and indispensable AA was greatest for casein compared to the other ingredients (P \u3c 0.05). Blood meal, plasma meal, and egg albumen had similar AID and SID of many AA. Egg albumen had the greatest AID and SID of Cys among ingredients, while plasma meal had greater AID and SID of Thr than blood meal (P \u3c 0.05). For experiment 3 (Exp. 3), potato concentrate, soy concentrate, soy isolate, and linseed meal were fed to 20, 25-kg barrows. The AID and SID of N was similar for potato concentrate, soy concentrate, and soy isolate and greater than linseed meal (P \u3c 0.05). The AID and SID of Leu and Thr were greater in potato protein concentrate than soy concentrate (P \u3c 0.05), and AID and SID of Thr was lower in soy isolate than potato concentrate. The apparent and standardized digestibility of all essential amino acids was similar between soy isolate and soy concentrate, and only the AID and SID of Asp was greater in soy isolate than soy concentrate (P \u3c 0.05). Linseed meal had the lowest AID and SID of N and AA digestibility among protein sources (P \u3c 0.05) in this experiment. In conclusion, animal protein and plant protein concentrates had the highest AID and SID of N and AA, and the digestibility of N and AA vary greatly among oilseed meals. As more grain by-products and alternative feed ingredients are being fed to livestock, researchers are determining the impact that fibrous components have on nutrient digestibility. Two experiments were conducted to determine the impact that different types of fiber have on the energy, nitrogen (N), and amino acid (AA) digestibility of soybean meal fed to growing pigs. In both studies, soybean meal served as the predominant form of amino acids for the animals, as the fibrous ingredients added little protein to the semi-purified, corn-starch based diets. A semi-purified, nitrogen-free diet (NFD) was used to estimate endogenous flows of AA. Pigs were surgically fitted with a simple T-cannula at the distal ileum and fed four experimental diets and the NFD on a 5 × 2 crossover arrangement in a randomized crossover design, with 5 diets and 2 periods. For experiment 1 (Exp. 1), soybean meal (SBM), SBM + corn hulls, SBM + rice hulls, and SBM + wheat straw were fed to 19, 45-kg barrows to determine apparent (AID) and standardized ileal digestibility (SID) of N and AA at the terminal ileum, apparent total tract digestibility (ATTD) of energy and N, and apparent hindgut digestibility (AHD) of energy and N. Rice hulls reduced the AID and SID of N, Arg, Ile, Thr, Trp, and Cys compared to the control and corn fiber diets and had lower AID of N and Glu and SID of N and Leu compared to the wheat straw diet (P \u3c 0.05). Wheat straw decreased the AID of Thr and Val compared to the control diet (P \u3c 0.05), but did not inhibit the SID of AA. The AID and SID of N and AA between the control and corn fiber diet were similar in the study. The inclusion of rice hulls reduced the AID of energy and N, the ATTD of energy, and the HAD of energy compared to the control group ( P \u3c 0.05). The AID, ATTD, and AHD of energy was lower in pigs fed wheat straw compared to the control diet (P \u3c 0.05); however, wheat straw did not influence N digestibility. The AID, ATTD, and HAD of N and energy of corn fiber was similar to the control. For experiment 2 (Exp. 2), sugar beet pulp was fed at four different inclusion levels (0 g/kg, 100 g/kg, 200 g/kg, and 300 g/kg) in soybean meal, cornstarch-based diets to 20, 35-kg barrows. Sugar beet pulp inclusion reduced the AID and SID of N and all indispensable and dispensable AA compared to the control diet (linear, P \u3c 0.05). The AID of energy and N were significantly reduced with sugar beet pulp was fed (linear and quadratic, P \u3c 0.05). Sugar beet pulp further reduced the ATTD of energy (linear and quadratic, P \u3c 0.05) and N (linear, P \u3c 0.05). There were no differences in AHD of energy and nitrogen among treatments. In conclusion, the SID and AID of N and AA and ATTD of energy and N is uniquely impacted by the source and inclusion level of fiber in diets fed to growing pigs