Highly-Processed Soy Protein Is an Alternative Protein Source to Fishmeal for Weaned Piglets

The objective of the study was to evaluate the effect of replacing fishmeal with highly-processed soy proteins with low content of anti-nutritional factors (ANF), AlphaSoy 530 (SP1), AlphaSoy (SP2), and HP 300 (SP3) on growth performance of weaned piglets. A total of 180 weaned piglets (JSR Genpacker and 90 PIC Camborough, initial BW 8.55 kg) were allocated randomly to 4 dietary treatments. There were 5 pigs/pen and 9 replicate pens/treatment (5 pens with barrows, 4 pens with gilts). Three diets based on wheat, barley, and SBM were fed from d 0 to 9 (Phase 1), d 9 to 22 (Phase 2) and d 22 to 36 (Phase 3). In Phase 1 and 2, fishmeal (6% and 3%, respectively) was replaced by 7.5% of either SP1, SP2, or SP3. A commercial grower diet without dietary treatments was fed to all groups in Phase 3. All diets in each phase were isocaloric and isonitrogenous. Growth performance was measured at d 9, 22 and 36. Diet, sex, and diet x sex served as fixed effects in the statistical model. No interaction of diet and sex was detected; therefore, only main effects are discussed. The in vitro enzyme digestible organic matter at ileal level was comparable among treatments in Phase 1 (84.2-85.9%) and Phase 2 (83-86.5%). The stachyose and raffinose content of diets was in the range of 0.92-1.43% (Phase 1) and 1.06–1.26% (Phase 2). The trypsin inhibitor activity was low in all treatments (Phase 1: < 0.5-0.5 mg/g; Phase 2: 0.5–0.6 mg/g). In Phase 1, pigs fed highly-processed soy proteins had a lower ADG and BW (except pigs fed SP2) compared to pigs fed fishmeal (P < 0.05). However, the FCR of pigs was the same between treatments (P > 0.1). In Phase 2, feeding SP1 diets improved FCR of pigs compared to feeding fishmeal (7% increase) or SP3 (10% increase) (P = 0.017). The growth performance of pigs was similar between treatments in Phase 3 and over the whole period - d 0 to 36 (P > 0.1). Barrows tended to have a lower FCR than gilts in Phase 2 and 3 and overall (d 0 to 36; P < 0.1); however, sex had no effect on other parameters (P > 0.1). In conclusion, highly-processed soy protein with low ANF, especially SP1 and SP2, is a good alternative protein source to fishmeal in the diet of weaned piglets.