Effect of heat increment and level of dietary energy and environmental temperature on the performance of growing-finishing swine.

Three experiments were conducted to evaluate levels and sources of dietary energy for growing-finishing pigs during cool and warm seasons. The specific objective was to determine the effect of lower energy diets containing more fiber during cooler temperatures. In Exp. 1, lower energy diets supported daily gains equal to those of pigs fed higher energy diets during low temperature trials, but gains were decreased (P less than .05) during high temperature trials. Feed conversion was improved with each increment of dietary energy and pigs were more efficient converters of feed during warm-season trials. Calorie utilization trends were not the same during cool and warm-season trials. Bermudagrass and alfalfa meal were used in lower energy diets in Exp. 2 and bermudagrass was used in lower energy diets in Exp. 3. Daily gains were not different in these trials, but trends in gain and feed conversion were similar to those in Exp. 1. In general, carcass traits did not differ significantly as a result of dietary treatment in these experiments. there was less (P less than .05) backfat on carcasses from low dietary energy groups during summer trials in Exp. 1 and 3. In all experiments, shoulder percentages were higher during warm-season trials. The data were combined with earlier data to illustrate dietary energy sources and levels and environmental temperature interactions and effects on average daily gain, and carcass traits. The response of gain, dressing, ham, belly and lean cut percentages as a function of metabolizable energy differed (P less than .05) between seasons. The effects of diet formulation and environmental temperature on growing pig performance and carcass traits are discussed.