26 Effects of increasing net energy or standardized ileal digestible lysine in soybean meal-based diets on early and late finishing pig performance

Abstract A total of 2,265 finishing pigs [337×1050, PIC; initial body weight (BW) = 50.2 kg) were used in two 28-d trials to determine the effect of increasing net energy (NE) or standardized ileal digestible Lys in soybean meal (SBM) based diets on early and late finishing pig performance. There were 27 pigs/pen and 21 pens/treatment. Soybean meal NE value used in diet formulation was either 78% (2,087 kcal/kg) or 100% (2,672 kcal/kg) of corn NE. Four treatment diets were assigned to pens in a completely randomized design and consisted of: 1) high level of SBM estimated at 100% NE of corn (High SBM); 2) low level of SBM estimated at 100% NE of corn with added feed-grade AA (Low SBM); 3) low level of SBM estimated at 78% NE of corn with added fat (Low SBM w/fat) to equal the NE in diets 1 and 2; and 4) low level of SBM estimated at 100% NE of corn with increased feed-grade AA and increased Lys:NE (Low SBM w/AA). Following the early finishing 28-d growth trial (initial BW = 50.2 kg), pigs were fed a common diet for 30-d and pens were randomly reallotted to 1 of the same 4 treatments for the late finishing trial (initial BW 114.1 kg). In early finishing, there were no differences (P > 0.10) in average daily gain (ADG), but pigs fed Low SBM w/AA had increased (P < 0.05) average daily feed intake (ADFI) compared with pigs fed High SBM (Table). The increased ADFI without increased ADG resulted in decreased (P < 0.05) gain to feed ratio (G:F) in pigs fed Low SBM w/AA compared with pigs fed Low SBM w/fat. Pigs fed Low SBM w/fat had improved (P < 0.05) caloric efficiency (CE) compared with pigs fed Low SBM w/AA. In late finishing, there was a tendency (P = 0.099) for a treatment effect on G:F where pigs fed High SBM had the greatest G:F, but there was not a significant difference (P > 0.05) between any two treatments when using a Tukey multiple comparison adjustment. There was no evidence (P > 0.10) for a difference between treatments on ADG, ADFI, or CE. Based on the performance of pigs fed the Low SBM w/AA diet, the decreased growth performance of low SBM diets is not due to a low Lys:Calorie ratio that results when NE is underestimated. Using caloric efficiency, an estimate of the NE of SBM was calculated by adjusting NE of SBM used in formulation until CE for the High SBM and Low SBM treatments were equal. These results showed SBM was estimated to contain 94% the NE of corn in the early finishing period and 125% the NE of corn in the late finishing period.