Weaning weight response of pigs to simple and complex diets

Five experiments were conducted to determine (1) the value of simple vs complex diets on gains and feed conversion of pigs weaned at a constant age but varying in weight, (2) the optimum postweaning time to change from a complex to a simple diet and (3) the effect of previous treatment on subsequent performance. In the first experiment, pigs were weaned at 3 wk +/- 3 d and assigned within four weight groups (4.1, 5.0, 5.6 and 6.7 kg) to a simple or complex diet that was fed for 28 d. The complex diet improved (P less than .01) pig performance in all weight groups. As anticipated, the heavier pigs (5.6 and 6.7 kg) ate more (P less than .02) and grew faster (P less than .03) than did their lighter weight littermates (4.1 and 5.0 kg). The second experiment involved pigs weaned at 3 wk +/- 3 d that were assigned within two weight groups (4.4 and 6.6 kg) and fed a complex diet for 10 d, after which one-half of each weight group was switched to a simple diet. Pigs fed the complex diet for the entire 24-d period gained faster (P less than .05) and were more efficient (P less than .05) than those changed to the simple diet after 10 d. The heavier weight (6.6 kg) pigs ate more (P less than .02) and gained faster (P less than .02) than did the lighter weight (4.4 kg) pigs.(ABSTRACT TRUNCATED AT 250 WORDS)