Evaluation of a bioprocessed soybean meal on nursery pig performance and immune status

A total of 239 pigs (initial BW 6.56 +/- 0.87 kg, 21 d of age) were used in a 35-d study to investigate the effects of fish meal (FM) and spray dried plasma (SDP) in combination with a bioprocessed soybean meal (SBM) on growth performance and immune responses in weaned pigs. Equal numbers of barrows and gilts were randomly allotted to 1 of 4 dietary treatments (10 pens/treatment) according to initial BW and sex: positive control (CON; corn/SBM diet) containing SDP and FM, the CON with bioprocessed SBM replacing FM (BPSBM+SDP), the CON with bioprocessed SBM replacing SDP (BPSBM+FM), and the CON with bioprocessed SBM replacing both SDP and FM (BPSBM). Experimental diets were fed in Phase I (d 1-7 post-wean) and II (d 8-21) followed by a common Phase III diet (d 22-35); changes in BW and feed disappearance were determined accordingly. Pigs were sensitized against ovalbumin (OVA) and Candida albicans (CAA) on d 7 and 21. Assessment of immune response was based on lymphocyte proliferation in response to mitogens Concanavalin A and phytohemagglutinin (d 14 post-wean), dermal hypersensitivity to OVA and CAA (% increase in local swelling at 2, 6, 24, and 48 h post-injection) on d 28, and primary and secondary anti-OVA IgG at d 21 and 28, respectively. Pigs fed CON were heavier (P < 0.01) than pigs fed BPSBM+FM and BPSBM, and not different from pigs fed BPSBM+SDP, at the end of Phase I and II (6.99, 6.80, 6.52, or 6.60 kg, pooled SEM 0.08, respectively in Phase I or 12.47, 12.18, 11.42, and 11.85 kg, pooled SEM 0.21, in Phase II, respectively). Hypersensitivity to OVA peaked at 2h in pigs fed CON, BPSBM+SDP, and BPSBM+FM or peaked at 6h in pigs fed BPSBM (121.4, 165.6, 139.0, and 144.1%, pooled SEM 22.9, respectively, at 2 h and 86.7, 114.5, 95.0, and 156.8%, pooled SEM 29.4, respectively at 6 h). Peak response to CAA occurred at 2h in all groups (42.6, 55.2, 48.2, and 50.6%, pooled SEM 11.9, respectively, in the CON, BPSBM+SDP, BPSBM+FM, and BPSBM, respectively). There was no difference in hypersensitivity due to experimental diet at any time point. Secondary anti-OVA IgG was 2-fold lower based on optical density values in pigs fed CON compared with BPSBM+FM and BPSBM (0.78 vs. 1.56 and 1.55 optical density at 405 nm, pooled SEM 0.42, respectively). Dietary treatment did not impact lymphocyte proliferation. The bioprocessed SBM is a suitable alternative for FM and/or SDP in Phase I and II nursery diets based on pig growth. The prolonged hypersensitivity to OVA indicate that bioprocessed SBM may have a positive impact on pig immune function and the 2-fold increase in anti-OVA IgG warrants further investigation on the impact of bioprocessed SBM on pig immune function.