Effect of the Dietary Net Energy Concentration on Feed Intake and Performance of Growing-finishing Pigs Housed Individually

The effect of dietary NE content on feed intake and performance of pigs was investigated using crossbred barrows with initial and final BW of approximately 35 and 110 kg, respectively. Pigs were housed individually and allowed ad libitum access to feed. Pigs were randomly allotted to 6 wheat and soybean meal-based diets (8.1, 8.7, 9.3, 9.9, 10.5, and 11.1 MJ NE/kg) with 16 pigs/diet. Ratios between standardized ileal digestible AA and NE were similar in all diets. Over the entire experiment, increase in dietary NE concentration was associated with a decreased ADFI (3.216, 3.216, 3.122, 2.910, 2.732, and 2.684 kg/d, respectively, for diets containing 8.1 to 11.1 MJ NE/kg; linear, P < 0.01). The NE intake increased as dietary NE increased from 8.1 to 11.1 MJ NE/kg (26.04, 27.98, 29.03, 28.81, 28.68, and 29.77 MJ/d, respectively; linear, P < 0.01, and quadratic, P = 0.06). Average daily gain increased when dietary NE concentration increased (1.046, 1.126, 1.135, 1.177, 1.156, and 1.152 kg/d, respectively, for diets containing 8.1 to 11.1 MJ NE/kg; linear and quadratic, P < 0.01). The increase in dietary NE concentration was associated with an increase in dressing percentage (76.5, 77.0, 77.4, 78.0, 78.2, and 78.4% of BW; linear, P < 0.01) but no differences in lean percentage (58.3, 57.9, 58.0, 57.3, 58.1, and 56.4% of HCW, respectively, for diets containing 8.1 to 11.1 MJ NE/kg; P = 0.12). When dietary NE concentration increased from 8.1 to 11.1 MJ/kg, the G:F increased (0.326, 0.352, 0.364, 0.405, 0.425, and 0.428 kg/kg, respectively; linear, P < 0.01), but the G:F expressed using the NE system did not change (G:F, 39.97 g/MJ NE; P = 0.44). When adjusted to the same dressing yield and lean percentage, the differences in adjusted ADG increased among treatments, but the adjusted G:F expressed using the NE system was not influenced by dietary energy concentration. These results confirm the ability of individually housed pigs to adjust their spontaneous feed intake over a very wide range of NE concentrations (8.7 to 10.5 MJ/kg). Under commercial conditions, pigs may experience less variation in ADFI than the results obtained in this experiment because of differences in dietary energy concentrations. However, it seems that only a severe reduction in dietary energy concentration will be effective in restricting energy intake of pigs that are allowed ad libitum access to feed.