DETERMINATION OF APPARENT ILEAL AMINO-ACID DIGESTIBILITY IN PEAS 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 peas (242 g crude protein/kg pea s, as-fed basis). Five barrows, average initial body weight 34.6 kg, w ere fitted with a simple T-cannula at the distal ileum and fed five di ets according to a 5X5 Latin square design. Diet 1 contained 885 g whe at/kg providing the sole source of dietary amino acids. Diets 2, 3 and 4 contained three graded levels of peas (168, 336 and 504 g/kg diet, respectively) and wheat (664, 443 and 221 g/kg diet, respectively). Di et 5 contained 671 g peas/kg diet, which provided the sole source of d ietary amino acids. All the diets were formulated to contain 160 g cru de protein/kg (as-fed basis). Chromic oxide (4 g/kg diet) was included as the digestibility marker. Each experimental period comprised 8 d. The pigs were fed twice daily, equal amounts, at 08:00 and 20:00 h. Th e dietary allowance was 1800 g/d. Ileal digesta were collected for a t otal of 24 h, at 2-h intervals, during d 7 and 9. Apparent ileal diges tibility values of amino acids in peas were determined with the direct method from diet 5, with the difference method from diets 2, 3 and 4 and with the regression method from diets 2, 3, 4 and 5, respectively. The accuracy of the determination of apparent ileal amino acid digest ibility values in peas with the difference method was dependent on the level of inclusion of the peas in the assay diet, as reflected by dif ferences in the standard errors of the digestibility values. There wer e no differences (P>0.05) in the digestibility values of peas when the se were determined with the direct, difference and regression methods. These results show that the apparent ileal digestibility values of am ino acids in feedstuffs with a medium-protein content, such as peas, c an be determined with either method, including the difference method w hen the inclusion level of the assay feedstuff is relatively high.