The response of the growing pig to changes in energy intake achieved through changes in dietary energy concentration versus restriction of feed intake

Abstract

This study was undertaken to compare the effects of changing energy intake, either by restricting feed intake or by altering dietary energy concentration, on the growth performance of pigs. The relative abilities of the DE, ME and NE systems to predict pig growth performance were also evaluated. A total of 72 barrows, having initial body-weights of 30 ± 2 kg, were randomly assigned to one of nine dietary treatments. These treatments were organized in a 3 x 3 factorial arrangement consisting of three dietary energy concentrations (2.18, 2.29 and 2.40 Mcal NE/kg) and three levels of feed allowance (80, 90 and 100% of ad libitum). Actual feed allowances of 79, 91 and 100% of ad libitum were achieved. No interactive effects of feeding level and dietary energy concentration were observed (P > 0.10). Increases in feed allowance from 79 to 91 to 100% of ad libitum resulted in increases in daily intakes of feed (P < 0.0001) and energy (P < 0.0001). Improvements in the rate (P < 0.0001) and efficiency (P < 0.0001) of body-weight gain were also noted. Additionally, feeding level affected the amount of energy available for body-weight gain on a daily (P < 0.0001) but not on a total (P > 0.10) basis. The efficiency with which dietary energy was used for weight gain was unaffected by feeding level (P > 0.10). Increases in dietary energy concentration were accompanied by decreases in daily feed intakes (P = 0.0016); however, dietary energy concentration did not affect daily energy intakes (P > 0.10). Neither average daily gains nor feed conversion efficiencies were affected by changes in dietary energy concentration (P > 0.10). Additionally, there were no differences among energy concentration treatments in terms of the amount of dietary energy available for body-weight gain (P > 0.10) or the efficiency with which it was used (P > 0.10). No differences were observed between the DE, ME and NE systems in terms of their abilities to predict the growth performance of pigs. The present study demonstrates that the energy intake of pigs can be effectively manipulated via adjustments in feeding level and that changes in dietary energy density, over the range studied here, are unable to affect changes in energy intake. This finding indicates that extreme caution should be used when extrapolating data obtained from studies in which feed allowance was manipulated to scenarios (e.g. commercial practice) in which energy density is to be altered, and vice versa.