Evaluation of a Bio-Processed 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 bio-processed soybean meal (MEPRO) on growth performance and immune responses in weaned pigs. Equal numbers of barrows and gilts were randomly allotted to one of 4 dietary treatments (10 pens/treatment) according to initial BW and sex: positive control (corn/soybean meal based diet) containing SDP and FM in combination (CON), SDP and MEPRO in combination (MEPRO_+SDP), FM and MEPRO in combination (MEPRO_+FM), and MEPRO. Experimental diets were fed in phase I (d 1-7 post-wean) and II (d 8-21) followed by a common diet in phase III (d 22-35). BW and feed disappearance were measured weekly. Pigs were immunized against ovalbumin (OVA) and Candida albicans (CAA) on d 7 and 21 post-wean. Assessment of immune response was based on dermal hypersensitivity to OVA and CAA (% increase in local swelling at 2, 6, 24, and 48 h post-injection) on d 28 post-wean, and primary and secondary anti-OVA IgG at d 21 and 28 post-weaning, respectively. Data were analyzed using Proc MIXED with pen as the experimental unit for performance and pig as the experimental unit for immune response. Pigs fed CON were heavier (P<0.01) than pigs fed MEPRO_+FM and MEPRO, and not different from pigs fed MEPRO_+SDP, at the end of Phase I and II (Phase I: 6.99, 6.52, 6.60, and 6.80 ± 0.08, and Phase II: 12.47, 11.42, 11.85, and 12.18 ± 0.21, respectively). Hypersensitivity to OVA peaked at 2h in pigs fed CON, MEPRO_+SDP, and MEPRO_+FM and peaked at 6h in pigs fed MEPRO (2h: 121.4, 165.6, 139.0, and 144.1 ± 22.9%, P=0.495, and 6h: 86.7, 114.5, 95.0, and 156.8 ± 29.4%, P=0.317, respectively). There was a prolonged hypersensitivity response to CAA in pigs fed MEPRO_+SDP, MEPRO_+FM, and MEPRO compared to CON (2h: 55.2, 48.2, 50.6, and 42.6 ± 11.9%, P=0.873, and 6h: 43.8, 37.5, 40.5, and 19.4 ± 14.2%, P=0.589, respectively). Secondary anti-OVA IgG was 2-fold lower in pigs fed CON compared to MEPRO_+FM and MEPRO (0.78 vs. 1.56 and 1.55 ± 0.42 OD_450nm, respectively). MEPRO is a suitable alternative for FM and/or SDP based on pig growth. The prolonged hypersensitivity response indicates an enhanced recruitment of T-cells to the site of inflammation suggesting MEPRO has an impact on pig immune function.