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Efficacy of soybean meal in reducing the effects of a PRRSv challenge in weaned pigs
The objective of our trial was to determine the efficacy of dietary soybean meal (SBM) in reducing the effect of a porcine reproductive and respiratory syndrome virus (PRRSv) challenge in nursery pigs as measured by immune response and growth performance. The two dietary treatments differed by method of supplying amino acids: either by SBM or synthetic amino acids (SAA) with SBM. Seventy-two mixed sex, weanling pigs (21 d of age, 10.83 ± 0.82 kg) were allotted by weight and sex to one of 18 pens in a completely random design. There were 4 pigs/pen and 9 observations/treatment. All pigs were fed the same industry-standard diet for 14 days, and then were fed one of two experimental diets for 10 days. All pigs were then inoculated both intramuscularly and intranasally with 1 mL each of live PRRS virus MN-184 (1X 106 fluorescent focus units (FFU)/mL dose) at 38 d of age (0 d post-inoculation, DPI). Blood was collected on 0, 3, 7, 14, and 28 DPI for determination of serum PRRSv load and cytokine concentrations. Pig BW and pen feed intake were recorded on blood collection days for the first 28 days and then bi-weekly until the termination of the trial at 125 kg BW. Pigs in the AA group tended to have lower TNF-α (Tumor Necrosis Factor-α) and IL-8 (InterLuekin-8) concentrations (P=0.100 and P=0.100) respectively on 0 DPI. At 3 DPI, pigs fed SBM vs. SAA had higher ADG (.613 vs. .299 kgs) (P=0.005) and G:F (.603 vs. .336) (P=0.0007). On 3 DPI, pigs fed the AA treatment tended to have lower IL-8 concentrations (117 vs 145 pg/mL) (P=0.08). Serum concentrations of INF-γ (Interferon Gamma) tended to be lower for the AA group at 7 DPI. At 14 DPI, serum concentrations of IL-4 (Interleukin-4) (P=0.025) were higher in pigs fed the SBM treatment. Pigs fed the AA diets had higher INF-γ concentrations on 14 DPI (P=0.034) and it tended to be higher (P=0.080) at 28 DPI. Results observed for growth performance and blood parameters were not consistent between treatments throughout the trial. While initial growth responses were improved by SBM diets, an overall increase in immune response was observed from pigs fed the AA based diets. Therefore, additional work needs to be done in clarifying the role of amino acid source in piglet growth and immune status
Keywords: Pigs, Soybean Meal, PRRSv