EFFECTS ON PERFORMANCE AND CARCASS CHARACTERISTICS OF NURSERY TO FINISHER PIGS FED REDUCED CRUDE PROTEIN, AMINO ACID-SUPPLEMENTED DIETS

An experiment was conducted to evaluate the effect of feeding reduced CP, amino acid (AA)-supplemented diets to pigs from weaning to slaught er weight on growth performance and carcass characteristics. Pigs were fed a 19%-16%-14% CP starter-grower-finisher high-CP sequence of diet s, respectively, or a sequence of diets reduced in CP by 4 percentage units (3 percentage units in the finisher period) with or without lysi ne (LYS), tryptophan (TRP), and threonine (THR) supplementation. Pigs fed the low-CP diets without AA supplementation grew more slowly, were less efficient in feed conversion, and developed carcasses that conta ined a smaller longissimus muscle, greater average backfat depths, and a lower percentage of muscle compared with pigs fed the high-CP seque nce of diets (P < .01). The reduction in growth performance, feed effi ciency, longissimus muscle area, and percentage of muscle in pigs fed the low-CP diets was alleviated by LYS, TRP, and THR supplementation ( P > .10). Although pigs fed the low-CP diets supplemented with AA had reduced average and 10th rib backfat depths compared with pigs fed the unsupplemented, low-CP diets (P < .01), these fat depth measures rema ined greater (P < .05) than those of pigs fed the high-CP diets. Feedi ng reduced dietary CP, regardless of AA supplementation, resulted in r educed heart (P < .10) and liver weights (P < .01) compared with feedi ng the high-CP diets. Although AA supplementation to the low-CP diets resulted in an increase in kidney weights relative to feeding the unsu pplemented low-CP diets (P < .01), kidney weights remained fewer than those of pigs fed the high-CP diets (P < .05). The data show that the reduction in pig performance and carcass muscle that resulted from fee ding reduced dietary CP can be corrected, providing that the proper am ine acids are supplemented.