GROWTH-PERFORMANCE OF WEANLING PIGS FED CORN-SOYBEAN MEAL DIETS WITH OR WITHOUT DRIED WHEY AT VARIOUS L-LYSINE.HCL LEVELS

A total of 490 crossbred weanling pigs were used to evaluate the responses to and the subsequent interaction between dietary dried whey and crystalline L-lysine.HCl on postweanling growth and feed efficiency at two periods postweaning. The experiment was conducted as a 2 x 5 factorial arrangement of treatments in a randomized complete block design to evaluate two levels of edible-grade dried whey (0 or 25%) and five dietary lysine levels ranging from 1.10 to 1.50% in .10% increments using a corn-soybean meal mixture as the basal feedstuff. Pigs were alloted by weight, litter, and sex to seven replicates at weaning (23 +/- 2 d) and fed their treatment diets for a 35-d period. Daily gain and feed intake were greater (P < .01) for both the 0- to 21- and the 22- to 35-d periods when dried whey was fed; the relative magnitude of the response to dried whey was greatest during the initial 21-d period. Growth responses during the 0- to 21-d period were, however, independent of dietary lysine level, suggesting that dietary lysine at a level of 1.10% is not the limiting nutrient in a corn-soybean meal diet or a corn-soybean meal diet with dried whey. From 22 to 35 d postweaning a linear growth response to lysine level occurred when the dried whey diet was fed, but no response was detected when lysine was added to the corn-soybean diet, resulting in a diet x lysine level interaction (P < .10). These results suggest that a component of dried whey other than lysine (e.g., lactose) was the most limiting nutrient in a corn-soybean meal-based diet, but when dried whey was supplemented, growth responses to crystalline lysine occurred during the latter phase of the starter period.