DETERMINATION OF APPARENT ILEAL AMINO-ACID DIGESTIBILITY IN BARLEY AND CANOLA-MEAL FOR PIGS WITH THE DIRECT, DIFFERENCE, AND REGRESSION METHODS

Three methods were evaluated for the determination of apparent ileal d igestibility values of amino acids in feedstuffs with a low protein (b arley, 10.2% CP) and a high protein content (canola meal, 38.2% CP). F ive barrows, average initial BW 40 kg, were fitted with a simple T-can nula at the distal ileum and fed five diets according to a 5 x 5 Latin square design. Diet 1 contained 42.7% canola meal providing the sole source of dietary amino acids. Diets 2, 3, and 4 contained three grade d levels of barley (22.5, 45.0, and 67.5%, respectively) and three gra ded levels of canola meal (36.6, 30.5, and 24.4%, respectively). Diet 5 contained 90.0% barley, which provided the sole source of dietary am ino acids. With the exception of diet 5, the diets were formulated to contain 16% CP. Chromic oxide (.4%) was included as the digestibility marker. The pigs were fed twice daily, equal amounts, at 0800 and 2000 . The dietary allowance was 1,800 g/ d. Each experimental. period comp rised 8 d. Ileal digesta were collected for a total of 24 h during d 7 and 8 at 2-h intervals. Apparent ileal digestibility values of amino acids in barley were determined with the direct method from diet 5, wi th the difference method from diets 2, 3, and 4, and with the regressi on method from diets 1, 2, 3, and 4. Digestibility values of amino aci ds in canola meal were determined with the direct method from diet 1, with the difference method from diets 2, 3, and 4, and with the regres sion method from diets 1, 2, 3, and 4. There were no differences (P >. 05) in the digestibility values in barley between the difference metho d when barley was included at 67.5% in the diet and the regression met hod. However, the digestibility values were lower (P <.05 or <.10) whe n these were determined with the direct method. There were no differen ces (P >.05) in the digestibility values of canola meal when these wer e determined with the direct method, the difference method, when canol a meal was included at 36.6% in the diet, and the regression method. I n conclusion, amino acid digestibility values in feedstuffs with a low protein content should be determined with the difference or regressio n methods rather than with the direct method. Amino acid digestibility values in feedstuffs with a high protein content can be determined wi th either method.