Determination of Sid Lys:ME Requirements in 129 to 149 Kg Pigs

A total of 990 pigs (PIC 337 X Camborough) were utilized to determine the SID Lys:ME (g/Mcal ME) requirement from 129 to 149 kg BW. Pigs were randomly allotted by BW to one of five SID Lys:ME levels (1.49, 1.73, 1.97, 2.21, or 2.45 g/Mcal ME) with 12 replicate pens/trt and 14 to 18 pigs/pen (0.85 to 1.10 m²/pig). The low and high Lys:ME levels were formulated as corn-SBM diets utilizing crystalline Lys, Thr, Met, and Trp to obtain the targeted Lys:ME and maintaining all other SID AA:Lys at 10% above NRC (2012) requirements. Diets were formulated to be iso-caloric (3,307 kcal ME/kg) and contained a minimum of 12% CP. Intermediate Lys:ME diets were made by blending the low and the high at appropriate levels to obtain the targeted Lys:ME levels. Dietary treatments were fed for 21 d. Statistical analysis to identify effects of dietary treatment were performed using the MIXED procedure of SAS. For break-point analysis, the NLMIXED procedure of SAS was utilized for linear broken-line regression in order to account for initial BW blocking; best fit statistics are presented based on R² values. Average daily gain did not differ among the Lys:ME levels (0.88 to 0.93 ± 0.02 kg/d, P = 0.475). Average daily feed intake was linearly reduced with increasing Lys:ME; linear broken-line analysis was beyond the scope of the trial parameters (P = 0.034). Feed efficiency (G:F) tended to increase as SID Lys:ME increased from 1.49 to 2.45 g SID Lys/Mcal ME (0.27 vs. 0.29 ± 0.01, respectively, P = 0.07); linear broken-line analysis indicated efficiency was maximized at 2.21 ± 0.01 g SID Lys/Mcal ME (P = 0.01; R² = 0.80). Data from this trial indicate that feed efficiency is optimized at 2.21 g SID Lys/Mcal ME in pigs weighing between 129 and 149 kg BW.