Digestibility of Amino Acids in Protein-Rich Feed Ingredients Originating from Animals, Peanut Flour, and Full-Fat Soybeans Fed to Pigs

SIMPLE SUMMARY: Dietary protein is a major contributing factor to animal feed cost. Recently, the overwhelming demand for and the unstable cost of conventional feed ingredients, such as soybean meal, have caused interest in alternative feed ingredients. By-products of agricultural industries may be cost-effective alternatives to conventional protein sources in swine diets. Therefore, to assess their full nutritional potential for pigs, it becomes necessary to evaluate the protein quality in alternative feed ingredients. In the present work, the digestibility of amino acids in four animal-derived protein sources (egg albumen, casein, blood meal, and blood plasma meal) and two plant-derived protein sources (peanut flour and full-fat soybean) were evaluated. Experimental diets were prepared to contain each of the test ingredients as the sole source of nitrogen and fed to growing pigs in two digestibility trials. The results of the experiments showed greater digestibility of amino acids in casein than the other animal protein sources. Digestibility of most amino acids in peanut flour was greater than in full-fat soybeans. Based on the current results, it is concluded that the test ingredients contain readily digestible amino acids which could make them useful in the diets of growing pigs. ABSTRACT: Standardized ileal digestibility (SID) of amino acids (AA) in alternative protein sources for growing pigs was determined in this study. Diets containing egg albumen (EA), casein, blood meal (BM), and blood plasma meal (BPM) and a nitrogen-free diet (NFD) were fed to 20 barrows in a quadruplicate 5 × 2 incomplete Latin square design with two periods in experiment 1. The SID of AA was greater in casein than other ingredients (p < 0.05), except Pro. The SID of Arg, Ile, and Met was lower (p < 0.05) in EA than BM and BPM. The SID of Trp in BM was greater (p < 0.05) than EA but not different from BPM. In experiment 2, 20 pigs were fed diets containing peanut flour (PF) or full-fat soybeans (FFSB) or NFD in a randomized complete block design with body weight as a blocking factor but providing six observations for NFD. The SID of Arg, Ileu, Leu, Met, Phe, and Val was greater (p < 0.05) in PF than FFSB. The SID of Lys was greater (p < 0.05) in FFSB than PF. In summary, the test ingredients contain readily digestible AA and could serve as alternative protein sources for growing pigs.