Study of the Yeast Cell Wall Components, Mannan Oligosaccharide and Beta Glucan, to Determine Their Individual and Synergistic Influence on Broiler Performance Under Pathologic Stress

Different supplementations or strategies have been proposed as alternatives to the use of antibiotics at sub-therapeutic levels in chickens. Mannan oligosaccharides (MOS) and β-glucans have been reported to beneficially influence broiler performance and health. However, different purifications levels have been employed to investigate the efficacy of those oligosaccharides, and thus conflicts have been noticed with respect to their influences. A series of studies were conducted to investigate the influence of purification, source, and individual components of yeast cell wall (YCW) on broiler performance subjected to pathogenic challenge. The challenge model included administration of 10x the recommended level of infectious bursal disease vaccine via the ocular route to all birds on day 10, in order to immunocompromise them. On days 16 and 17, birds in all treatments except non-challenged control received 3 mL of 10^7 cfu of Clostridium perfringens (Cp). Broiler performance was evaluated on days 10, 16, and 21. In study 1, tissue samples were collected from the jejunum and duodenum regions for analysis with a chicken-specific peptide arrays technique to study the influence of YCW supplementation on the immune and metabolic pathways. The Cp challenge significantly impacted broiler performance in all studies. The purification level of YCW preparations had different levels of influence on performance as well as metabolic pathways. The addition of purified YCW to the starter broiler diets improved performance and influenced the immune and metabolic pathways in the gut. In the second study, two experiments were conducted with different levels of highly purified β-glucan from algae (Euglena gracilis) or highly purified MOS from Saccharomyces cerevisiae. Addition of no more than 30 ppm of algae β-glucan was sufficient to improve broiler performance; however, no significant differences were observed in performance with any of the MOS levels. The third study evaluated the influence of mannoproteins or β-glucan preparations purified at 50-55%, derived from the same YCW product of Saccharomyces cerevisiae individually or in combination. The performance of starter broilers was improved when a combination of mannoprotein and β-glucan was added to the diet. The last study evaluated the influence of two YCW products prepared from two different strains of Saccharomyces cerevisiae on full-term broiler performance for birds reared on reused floor litter. The products were supplemented at either 250 ppm continuously or 500, 250, and 125 ppm in the starter, grower, and finisher phases, respectively. Broiler performance positively responded to YCW products and both feeding strategies. Overall, purification and source of β-glucan and MOS have significant impacts on broiler response, and those components have synergetic influence when combined