Effect of Dietary Net Energy and Digestible Lysine Levels on Growth Performance and Carcass Composition of Finishing Pigs

Studies evaluating the optimal dietary NE levels or standardized ileal digestible (SID) Lys:NE ratios in diets for finishing pigs are scarce. An experiment was conducted to evaluate the effects of dietary SID Lys and NE levels on performance and carcass composition of 60- to 100-kg pigs. A total of 288 mixed-sex pigs (PIC GP1050; initial BW of 59.2 ± 0.44 kg) were assigned to 6 dietary treatments with 8 pen replicates (3 barrows and 3 gilts/pen) per treatment using a 2 × 3 factorial arrangement with 2 levels of SID Lys (0.70 or 0.80%) and 3 NE levels (9.40, 9.75 or 10.10 MJ/kg) for 45 d. Diets were formulated based on corn, soybean meal and wheat bran using the analyzed ingredient AA contents and published SID coefficients to meet ideal AA ratios. Pigs had ad libitum access to feed (mash) and water. Individual pigs and pen feed disappearance were weighed on bi-weekly basis to calculate ADG, ADFI and G:F. All pigs were slaughtered for carcass assessment after reaching approximately 107 kg BW. Data were analyzed using the GLM procedure of SAS. There were no SID Lys × NE interaction effects (P > 0.05) for any performance or carcass parameter. The ADFI was not affected (P > 0.10) by the dietary SID Lys (2128 and 2007 g/d) or NE levels (2103, 2035 and 2065 g/d). Both ADG and G:F seemed to maximize at 0.80% SID Lys and 9.75 MJ NE. However, ADG and G:F were not affected by the NE levels. Increasing the SID Lys from 0.70 to 0.80% increased (P < 0.05) both the ADG (854 and 892 g/d) and G:F (0.418 and 0.460). Increasing SID Lys from 0.70 to 0.80% tended to reduce (P = 0.06) the amount of NE needed per kg BW gain from 24.3 to 22.1 MJ/kg BW gain. The SID Lys efficiency (g/kg of BW gain) was not affected (P > 0.05) by both Lys and NE levels. Supplying 0.80% SID Lys in the diets reduced the number of days on trial to reach the slaughter BW by about 3 d compared with 0.70% SID Lys. Carcass yield maximized at a dietary NE content of 9.75 MJ/kg. Carcass leanness and backfat thickness were not affected by dietary treatments. Overall, both performance and carcass composition optimized when the diet contains 0.80% SID Lys and 9.75 MJ/kg NE, which corresponds to 0.82 g SID Lys/MJ NE.