Availability to pigs of amino acids in cereal grains. 3. A comparison of ileal availability values with faecal, chemical and enzymic estimates

1. Availability values for amino acids in nine cereal grains determined by faecal analyses with pigs and by the Silcock available lysine test (Roach et al. 1967) and an in vitro digestibility assay were compared with ileal availability values for the same grains determined with pigs by Taverner et al. (1981 b). 2. There was a significant canonical correlation of ileal and faecal availability values. On average, apparent faecal availability of the indispensable amino acids was 4.2% greater than apparent ileal availability, but the difference was up to 12.6% for threonine. Furthermore, the difference appeared to increase as the digestibility of the grain decreased. 3. Silcock available-lysine values for the cereal grains were unrelated to the lysine truly absorbed by the pig. 4. There were close relationships of ileal protein and lysine availability values of nitrogen digestibility determined by an in vitro assay using pronase enzyme.