Abstract Porcine reproductive and respiratory syndrome virus (PRRSv) is a viral respiratory disease of pigs that causes significant economic impact, resulting in an annual loss of over 1. 2 billion to the US pork industry. Despite the presence of different control measures, the disease remains widely distributed, prompting the search for alternative control measures. Feed additives have shown promising results in some preliminary pig trials. Therefore, the objective of this study was to evaluate the effects of different yeast-derived products against PRRSv in experimentally challenged nursery piglets. Piglets weaned at 21 days of age from PRRSv-free sow herds were randomly assigned to one of five treatment groups with 20 piglets per group. Piglets were fed either a control diet (CON) or a diet supplemented with a yeast cell wall fraction with mannans and beta-glucans at or around 20% each (YCW, 1 kg/ton), a 50% yeast beta-glucans fraction without mannans (BG, 250 g/ton), active dry yeast (ADY, 1 kg/ton), or 3-strain Bacillus probiotic blend (BAC, 1. 25 × 10⁶ CFU/g feed) from 0 to 42 days post-weaning. On day 14 all piglets were challenged with PRRSv-2 strain 1-4-4 via intramuscular injection at a dose of 10³ TCID50. Mortality and body temperature were measured daily. Performance parameters and blood samples were collected weekly. PRRS virus titers were measured in the blood using qPCR. Data was analyzed using one-way ANOVA, followed by Tukey's post hoc analysis for pairwise comparisons. A two-tailed binomial analysis was also conducted to identify differences in mortality percentages. Piglets supplemented with YCW had significantly lower body temperature (p 0. 001) on day 6 post-challenge and improved body weight gain (p 0. 01) during the week following the challenge (days 15-21). Piglets supplemented with BG had numerically lower viral load in the blood, leading to a significant decrease in mortality (p = 0. 07). There were no significant effects of LY and BAC in this trial (P 0. 10). The results showed that the YCW was able to decrease fever and inflammation, resulting in improved performance, while BG was able to decrease viral load and mortality, possibly through its immunomodulatory effect. In conclusion, the findings of this study suggest that specific yeast-based feed additives can be effective in mitigating the negative impacts of a PRRSv challenge in nursery piglets providing a potential alternative to current control measures.
Gebreyohannes et al. (Wed,) studied this question.
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