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Impact of hydrolyzed yeast product in nursery pig diets on growth performance and immune response
CELMANAX SCP is an enzymatically hydrolysed yeast product containing yeast culture and other complex carbohydrates. This study was conducted to assess the impact of CELMANAX SCP on weaned pigs’ growth performance and immune response and to define the optimal dietary inclusion level in nursery diets containing antibiotics. Ninety-six nursery (6.29 ± 0.22 kg BW; n = 12 pens/treatment) pigs were assigned to one of 4 dietary levels of CELMANAX SCP (0.0, 0.01, 0.02, and 0.04%) in a 2-phase feeding program for 49d post-wean. Pig weight gain and pen feed disappearance were measured weekly. Immune response was assessed based on dermal hypersensitivity to ovalbumin (OVA) and production of anti-OVA antibodies. Vaccinated pigs were immunized, by intramuscular injection, to induce antibody response and hypersensitivity on d 27 and 41 post-weaning (0.5 mg OVA and 0.5 mg Quil A in 1 mL phosphate buffer). Blood samples were obtained on d 27, 41, and 49 for determination of anti-OVA IgG antibodies. Dermal hypersensitivity was determined on d 49 where all pigs were given 200 µg OVA in 50 µL saline by intradermal injection in the ear. Ear thickness measurements were made using a spring-loaded caliper at 2, 6, and 24 h after injection. All pigs performed similarly throughout the study where final BW was 32.2, 33.3, 31.9, and 32.0 ± 1.0 kg in pigs fed increasing levels of dietary CELMANAX SCP. Overall daily gain (0.51, 0.55, 0.52, and 0.53 ± 0.02 kg/d), feed disappearance (0.82, 0.86, 0.86, and 0.85 ± 0.02 kg/d), and gain:feed (0.62, 0.64, 0.61, and 0.62 ± 0.01) was not affected by increasing dietary inclusion of CELMANAX SCP. There was a linear effect of time (P < 0.001) on anti-OVA IgG where optical density increased with time. There was no effect of diet on anti-OVA IgG. There was a linear effect of time (P < 0.001) on ear thickness where ear thickness decreased over time from 2 to 24 h. There was a trend (P = 0.084) to an interaction between CELMANAX SCP inclusion and time on ear thickness where ear thickness was not different from 6 to 24 h in pigs fed 0.04% CELMANAX SCP and declined over time for all other groups. There was no quadratic effect of time, diet, or their interaction on anti-OVA IgG or ear thickness. Dietary inclusion of CELMANAX SCP did not affect pig growth performance but appears to positively impact immune response.
Keywords: immune response, growth performance, nursery pigs