APPARENT AND TRUE AVAILABILITIES OF AMINO ACIDS IN WHEAT AND MILLING BY-PRODUCTS FOR GROWING PIGS

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Abstract
The apparent availabilities of amino acids measured by the ileal and fecal analysis methods, in wheat, flour and a diet consisting of 45% bran, 45% shorts and 10% middlings (wheat offal), and the metabolic ileal and fecal amino acid levels from protein-free diets containing 5, 10 or 15% alphafloc were determined with barrows ranging in weight from 45-70 kg. Availabilities of amino acids, by either method of determination, declined from the flour to the whole wheat to the wheat offal diets for all except arginine by the ileal method. Overall, availability as determined by the fecal method was higher than by the ileal method, and in the majority of comparisons the difference was significant. Lysine and threonine were the least available of the indispensable amino acids by either method of determination. Because of their relatively large disappearance in the large intestine, the availabilities of threonine in all diets tested and of lysine in wheat offal may not be accurately determined by the fecal analysis method. As the level of alphafloc in the protein-free diets was increased, ileal and fecal amino acid levels, expressed as grams per kg dry matter intake, increased. The metabolic amino acid levels were found to increase for isoleucine, leucine, lysine, methionine and aspartic acid and to decrease for glycine and proline between the end of the ileum and feces.