Comparative Efficacy of Different Soy Protein Sources on Growth Performance, Nutrient Digestibility and Intestinal Morphology in Weaned Pigs

To elucidate the efficacy of different soy protein sources on piglet's performance, a total of 280 weaned piglets ($Duroc{\times}Yorkshire{\times}Landrace$, $23{\pm}3$ d of age, $5.86{\pm}0.45$ kg initial BW) were allotted to 5 treatment diets comprising soybean meal (SBM), soy protein concentrate (SPC), Hamlet protein (HP300), fungal (Aspergillus oryzae) fermented soy protein (FSP-A), and fungal plus bacterial (A. oryzae+Bacillus subtilis) fermented soy protein (FSP-B), respectively. Experimental diets for feeding trial were formulated to contain each soy protein sources at 8% level to corn-whey powder basal diet. There were 14 pigs per pen and 4 pens per treatment. Experimental diets were fed from 0 to 14 d after weaning and then a common commercial diet was fed from 15 to 35 d. Also for ileal digestibility studies, 18 pigs were assigned to 6 dietary treatments as N-free, SBM, SPC, HP300, FSP-A and FSP-B with T-canulation at distal ileum for 6 days. At $14^{th}$ d of experimental feeding, the ADG was significantly higher (p<0.05) in SPC fed diet as compared with others. Similar trend was noticed during the 15-35 d and overall study (0-35 d). All the processed soy protein sources tested in this experiment improved (p<0.05) growth than SBM during overall study. The nutrient digestibility of GE, DM, CP and Ca showed lower (p<0.05) values in SBM and FSP-A fed groups than SPC and FSP-B treatments. The apparent ileal digestibility of TEAA, non-TEAA and TAA showed lower (p<0.05) in SBM treatments compared with other soy protein sources. The true ileal digestibility of TEAA, non-TEAA and TAA were lower (p<0.05) in SBM fed group than SPC and HP300 treatments, and lower than FSP treatments though they didn't achieve significant difference (p>0.05). Villous height and crypt depth was not affected by dietary treatments. In conclusion, the growth and digestibility of nutrients in weaned pigs fed SPC was superior to others. Also FSP-A and FSP-B showed improved performance than those fed SBM.