143 Effect of increasing dietary net energy content at a constant lysine on feed intake and performance of 7 to 11 kg and 11 to 20 kg pigs

Abstract Information about NE requirements for nursery pigs is still limited. Therefore, 2 experiments were conducted to evaluate the effect of dietary NE contents on growth performance of 7 to 11 kg pigs (Exp. 1) and 11 to 20 kg pigs (Exp. 2). In Exp. 1, mixed-sex pigs (n = 192; PIC; initial body weight (BW) of 7.8 ± 1.07 kg] were assigned to 4 diets for 14 d. Diets 1 to 4 were formulated to contain 4 levels of NE (9.8, 10.1, 10.4 and 10.7 MJ/kg) and adequate in all AA with standardized ileal digestible (SID) Lys being constant at 1.42%. In Exp. 2, mixed-sex pigs (n = 192; PIC; initial BW of 11.2 ± 1.54 kg) were assigned to 4 diets for 21 d. Diets 1 to 4 contained 4 levels of NE (9.6, 9.9, 10.2 and 10.5 MJ/kg) and adequate in all AA (1.32% SID Lys). For both studies, there were 6 pen replicates (4 entire males and 4 gilts/pen) per treatment, and diets were based on corn, soybean meal, whey powder, wheat bran and soy oil. Pigs had ad libitum access to feed (mash) and water. Individual pigs and pen feed disappearance were weighed weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency gain to feed ratio (G:F). Data were analyzed by ANOVA using the GLM procedure of SAS with pen as the experimental unit. In Exp. 1, ADFI tended to decrease (quadratic; P ≤ 0.08) with increasing NE levels during d 0 to 7 and d 8 to 14. The ADG during d 0 to 7 tended to be greater (158, 192, 187 and 152 g for diets 1 to 4; quadratic; P = 0.08) at 10.1 MJ/kg NE; however, the overall ADG (d 0 to 14) was not affected by the NE levels. Although not significant, G:F, Lys utilization efficiency were greatest at 10.1 MJ/kg NE for the overall period. In Exp. 2, ADFI decreased (827, 783, 768 and 749 g for diets 1 to 4; linear; P = 0.05) with increasing NE levels during d 15 to 21 but was not affected (P 0.05) for other periods. The ADG (d 8 to 14) tended to be greater at 9.6 MJ/kg NE (quadratic; P = 0.06) and G:F (d 15 to 21) tended to be greater at a dietary NE of 10.2 MJ/kg (linear; P = 0.10). However, the overall (d 0 to 21) ADG and G:F were not affected (P 0.05) by NE levels. Although not significant, G:F and Lys utilization efficiency were greatest at a dietary NE of 10.2 MJ/kg for the overall period. These results indicate that G:F of 7 to 11 kg pigs and 11 to 20 kg pigs maximized at a dietary NE content of 10.1 MJ/kg and 10.2 MJ/kg, which correspond to 1.41 and 1.29 g SID Lys/MJ NE, respectively.