THE EFFECT OF DIETARY CRUDE PROTEIN LEVEL ON AMINO-ACID DIGESTIBILITYIN EARLY-WEANED PIGS

Studies were carried out with 12 pigs (Yorkshire x Landrace), weaned a t three weeks of age, to determine the effect of the dietary level of crude protein on the ileal and fecal digestibilities of protein and am ino acids. The pigs, fitted with a simple T-cannula at the distal ileu m, were fed four com starch-based diets formulated to contain 16.5, 19 .5, 22.5 and 25.5 % crude protein from soybean meal according to a bal anced two-period change-over design. The pigs were fed four times dail y, equal amounts at 02.00, 08.00, 14.00 and 20.00 h, at a rate of 5 % (w/w) of the average body weight which was determined at the initiatio n of each experimental period. Each experimental period lasted 9 d. Fe ces were collected on d 6 and d 7; ileal digesta on d 8 and 9. Chromic oxide was used as digestibility marker. There were no differences (P > .05) in the apparent ileal digestibilities of protein and amino acid s between dietary treatments. The average of the ileal digestibilities of the indispensable amino acids were 84.1, 84.6, 83.3. and 83.2 % fo r the diets containing 16.5, 19.5, 22.5 and 25.5 % crude protein, resp ectively. However, there was a linear decrease (P < .05), based on pol ynomial regression analysis, in the ileal digestibilities of the major ity of amino acids as the dietary protein level was increased. The fec al amino acid digestibilities were not affected (P > .05).