الملخص
Background: The increase in use of alternative feeding practices as a result of the ban on antibiotics as growth promotors has led to an increased demand for safe and sustainable feeding strategies that improve immune function and promote animal health. Saccharomyces cerevisiae based supplements that have been treated to be inactive are well documented to modulate the immune system through the bioactive molecules present within them, which include; β-glucans, mannan oligosaccharides (MOS), nucleotides, peptides, vitamins, and various other functional metabolites. Although there is an increasing trend toward using these products in animal nutrition research, there is limited data available about the immunological effects from orally administered dosages of Thepax ®, an intact inactivated yeast product, at different levels in small ruminant species.
Objective: The purpose of this study was to determine the effect of two different doses of orally administered Thepax ® on humoral and cellular immunity in both healthy sheep during a 90-days experimental period.
Methodology: We used a controlled study with thirty healthy sheep aged from 3-12 months, randomly distributed into three treatment groups with ten in each. Sheep in the "low dose" group received 10 ml/day of Thepax® this dose contained approximately 100 billion (1 × 10¹¹) inactivated but structurally intact yeast cells and less than 1 × 10⁴ colony-forming units (CFU) of viable cells.; sheep in the "high dose" group received 20 ml/day of thepax contained approximately 200 billion (2 × 10¹¹) inactivated but structurally intact yeast cells and less than 2 × 10⁴ CFU of viable cells. Sheep in both treatment groups were compared to sheep that had been administered an equal volume of sterile physiological saline. Blood was sampled on day zero prior to treatment and then every 10 days thereafter for ninety days. Using commercial ELISA kits, we determined serum concentrations of IgG, IgM, and IgA. Phagocytic activity as a measure of cellular immunity was also measured. Repeated measures analysis of variance (repeated measures ANOVA) followed by a Tukey’s Multiple Comparison Test was performed on the data, with p<0.05 being considered statistically significant.
The results demonstrated that oral supplementation using Thepax resulted in a marked enhancement of humoral immunity over the duration of the trial. IgM, IgG and IgA levels continued to increase throughout the course of the trial in each of the treated groups while there was little or no indication of temporal variation in the controls. In addition, we found a consistent increase in antibody response from the high dosage treatment as compared to the low dosage treatment. This finding clearly indicates a dose dependent stimulation of the immune system (P<0.001). We also observed an improvement in the phagocytic index post-oral ingestion of Thepax; this finding suggests an improvement in the innate cellular components of the immune system. Analysis by repeated measures ANOVA showed statistically significant main effects for treatment, sampling time and for the interaction of treatment x sampling time on all of the immunologic parameters assessed (P<0.001).
Conclusion: When Thepax(r) is administered orally, it increases both humoral and cellular immune responses in sheep; the extent to which these immune responses are increased will depend upon how much Thepax(r) was administered. Therefore, based upon these results, there is some evidence that structurally intact inactivated Saccharomyces cerevisiae may be used as a functional feed additive to enhance immune function in small ruminant animals. Thus, there exists an empirical basis for conducting additional studies examining the potential of this product to protect against diseases and improve the health status and productivity of sheep within commercial production systems.