The effects of genetic variation at r, rb and Tri loci in Pisum sativum L. on apparent ileal digestibility of amino acids in young broilers

The nutritional effect of genetic variation at r and rb loci was investigated by determining apparent and true amino acid digestibility of four near-isogenic lines of pea (RRRbRb, RRrbrb, rrRbRb, rrrbrb) fed to young broilers in a metabolism study. The results demonstrated that the round-seeded line (RRRbRb) generally had the lowest amino acid content with, for example, 2.5 g cystine kg^-1 dry matter (DM) and 1.6 g methionine kg^-1 DM, compared with contents in the three wrinkled-seeded lines (rrRbRb, RRrbrb and rrrbrb). The double mutant line (rrrbrb) generally had the highest amino acid content, with 3.2 g cystine kg^-1 DM and 2.3 g methionine kg ^-1 DM, and an elevated amino acid content compared with the single mutant lines (RRrbrb, rrRbRb). However, the round-seeded line (RRRbRb) consistently had the highest coefficient of true (CTID), and apparent (CAID), ileal digestibility for all amino acids (e.g. 0.959 and 0.928 respectively for CTID and CAID for methionine) when compared with the three wrinkled lines RRrbrb, rrRbRb and rrrbrb (0.853, 0.877 and 0.866, respectively, for CTID, and 0.862, 0.882 and 0.874 for CAID). A second experiment examined the digestibility of amino acids in a pair of lines, HC8 and LC8, near-isogenic except for the locus controlling the concentration of seed trypsin inhibitor (H, high; L, low). The results showed that the CAID and CTID obtained for all amino acids were consistently higher for LC8 than for HC8 (for methionine: 0.905 and 0.709 for CTID, respectively, for LC8 and HC8; 0.887 and 0.729, respectively, for CAID), indicating the very specific effects of quantitative variation in these proteins on nutritional value of peas for poultry.