The Effect of Feeding Processed Soy Protein on the Growth Performance and Apparent Ileal Digestibility in Weanling Pigs

For Exp. 1, one hundred twenty Duroc${\times}$ Yorkshire${\times}$Landrace pigs (6.34${\pm}$ 0.70 kg average initial BW) were used in a 35 d growth assay. There were six pigs per pen and four pens per treatment. Dietary treatments included 1) NC (negative control; basal diet), 2) PC (positive control; added 5% HP $300^{(R)}$, HAMLET PROTEIN A/S, as protein source), 3) PSP 2.5 (added 2.5% $Pepsoygen^{(R)}$, Genebiotech Co. Ltd., as protein source), 4) PSP 5.0 (added 5% $Pepsoygen^{(R)}$ as protein source), and 5) PSP 7.5 (added 7.5% $Pepsoygen^{(R)}$ as protein source). For d 21, ADFI was increased in pigs fed PSP diets compared with PC diet (p<0.05). ADG was tended to improve as concentration of PSP in the diets was increased. For d 21-35 and entire experimental period, pigs fed PSP diets had more feed intake than pigs fed NC or PC diets (p<0.05). For the whole period, ADG was improved in PSP treatments compared with NC treatment (Linear effect, p=0.05). On d 21 and d 35, digestibilities of DM and N were higher (p<0.05) for pigs fed PSP diets than pigs fed NC diet and PSP 2.5 treatment was the highest among the treatments. On d 21, digestibility of N was significantly improved in PSP treatments compared with PC treatment (p<0.05). For Exp. 2, five Duroc${\times}$Yorkshire${\times}$Landrace barrows (8.74${\pm}$0.22 kg average initial BW) were surgically fitted with a simple T-cannulas approximately 15 cm prior to the ileo-cecal junction. The experimental designs were 5${\times}$5 latin squares with pigs and periods as blocking criteria. Dietary treatments were same as Exp.1. Generally, apparent ileal digestibilities of DM and N were higher for pigs fed PSP diets than pigs fed NC or PC diets (p<0.05) and PSP 5.0 and 2.5 treatments were the highest among the treatments, respectively. Apparent ileal digestibilities of the whole amino acids were increased in PSP treatments compared with NC treatment (Quadratic effect, p${\leq}$0.05). Also, histidine, lysine and threonine digestibilities in essential amino acids and alanine, asparatic acid and glycine digestibilities in non essential amino acids were significantly higher for pigs fed PSP diets than pigs fed PC diets (p${\leq}$0.05). In conclusion, feeding processed soy protein to weanling pigs increased growth performance, nutrient digestibility and apparent ileal digestibilities of DM, N and most amino acids.