Effects of Replacing Soy Protein Concentrate with Fermented Soy Protein in Starter Diet on Growth Performance and Ileal Amino Acid Digestibility in Weaned Pigs

For Exp. 1, 120 ((YorkshirexLandrace)xDuroc) weaned pigs (7.96 +/- 0.01 kg average initial BW, 21 days weaning) were. used in a 28 d-growth assay to determine the effects of replacing soy protein concentrate (SPC) with fermented soy protein (FSP) in a starter diet (d 0 to 7) on the growth performance, apparent fecal amino acid digestibility and subsequent performance in weaned pigs. Dietary treatments included: i) FSP0 (basal diet; whey-skim milk powder-SPC based diet): ii) FSP5 (replacing SPC with 5% FSP): iii) FSP10 (replacing SPC with 10% FSP). Pigs were fed the phase I diet for 7 days, and then each group was fed a common commercial diet for 21 days to determine the effect of previous diet on subsequent performance. Average daily gain (ADG) from d 5 to 7 (linear effect, p = 0.01) and d 7 to 14 (linear effect, p<0.001) were increased as FSP level increased. The pigs fed with FSP was heavier than the pigs fed with SPC at d 5 to 7 and d 7 to 14 after weaning (p<0.05). In the entire period (d 0 to 28), there were no significant difference; in weight gain and final weight between SPC and FSP diets (p>0.05). Average daily feed intake (ADFI) was higher in pigs fed with the 5% FSP diet than those fed with the other diets at d 0 to 2 post-weaning (quadratic effect, p = 0.05). Also, for the entire period of phase I (d 0 to 7), pigs consumed more 5% FSP diet compared to other treatments (quadratic effect, p = 0.03). Gain/feed (G/F) was not affected by dietary SPC or FSP in phase I and subsequent periods, but G/F from d 5 to 7 after weaning was improved linearly (p = 0.04) as dietary FSP level increased. Pigs fed with 10% FSP also improved G/F compared with those fed only SPC (p<0.05). At d 7, there were linear increments in fecal dry matter (DM) (p<0.1) and nitrogen (N) (p<0.01) digestibilities as the dietary FSP level increased. The. digestibilities of fecal essential and total amino acids were increased as the FSP level increased (linear effect, p<0.1). For Exp. 2, three ((YorkshirexLandrace)xDuroc) weaned barrows (average initial BW of 7.32 kg) were surgically fitted with a simple T-cannula approximately 15 cm prior to the ileo-cecal junction. The experimental designs were 3x3 latin squares with pigs and periods as blocking; criteria. Dietary treatments and composition were the same as in Exp. 1. Apparent ileal N digestibility was increased as FSP level was increased (linear effect, p<0.05). The dietary treatments (SPC and FSP) did not affect apparent ileal DM digestibility (p>0.05). Among essential amino acids, apparent digestibility of ileal arginine (Arg), lysine (Lys), methionine (Met) and phenylalanine (Phe) were improved as the FSP level increased (linear effect, p<0.1). Also, apparent ileal total essential, non-essential and total amino acid digestibilities were increased linearly (p<0.1). In conclusion, replacing SPC with fermented soy protein appeared beneficial in growth performance, N and amino acid digestibility during the early 7 days after weaning, and an equivalent effect showed on growth performance in subsequent period of 7 to 28 days after weaning.