Effect of extrusion on the ileal and fecal digestibilities of lysine, nitrogen, and energy in diets for young pigs

Forty crossbred barrows (initial average BW of 20 kg) were fitted with T-cannulas in the distal ileum to determine the effects of extrusion of soybean meal on the apparent ileal and fecal digestibilities of lysine, N, and GE. A basal corn-soybean meal diet was formulated to contain .525% lysine. Nonextruded soybean meal (SM), extruded soybean meal (ESM), and L-lysine.HCl (LLH) replaced cornstarch in the basal diet to make diets containing .60, .675, and .75% total dietary lysine for each lysine source. Treatments were arranged as a 3 x 3 factorial with the basal diet as an additional treatment. Ileal and fecal digestibilities of lysine were not affected (P greater than .05) by source of lysine. However, linear increases (P less than .05) occurred in ileal lysine digestibilities with increasing concentrations of dietary lysine provided as LLH, but not when lysine was provided as SM or ESM. Apparent ileal and fecal retention of N as percentages of N absorbed or consumed were greater (P less than .05) for diets containing LLH than for diets containing SM, and diets containing ESM were intermediate. Linear increases (P less than .05) occurred in ileal and fecal N retained as percentages of N absorbed or consumed with increasing concentration of dietary lysine provided as LLH or ESM, but not when provided as SM. Fecal DE and ME (kilocalories per gram of diet) for diets containing LLH and ESM were similar and greater (P less than .05) than the values obtained for diets containing SM.(ABSTRACT TRUNCATED AT 250 WORDS)