Abstract
Different supplements or strategies have been proposed as alternatives to the use of antibiotics at sub-therapeutic levels in chickens. Mannan oligosaccharides and β-glucans, yeast cell wall fractions (YCW), have been reported to beneficially influence broiler performance and health. Two differently produced yeast cell wall fractions derived from Saccharomyces cerevisiae were evaluated in this study using two different supplementation strategies offered to full-term broilers. The birds were placed in floor pens on used pine-shaving litter to increase potential microbial stress and mimic industry practice. The study utilized a three-phase feeding program with a 1- to 21-day starter, 21- to 35-day grower and 35- to 42-day finisher phases. Five dietary treatments were compared in this study. The experimental diets consisted of a control basal broiler diet; or the basal diet supplemented with the two differently produced fractions of YCW. The YCW products were supplemented at a constant 250 ppm or a decreasing concentration program (500, 250, 125 ppm) throughout the three feeding phases. Birds fed diets supplemented with either YCW products at any inclusion regimen demonstrated higher (P < 0.05) body weight (BW) in all three phases than control birds. The difference in final 42-day BW of the YCW treatments (3041 g) averaged 165 g higher (P < 0.05) than the control group. For all YCW treatments, productivity index was higher (P < 0.05) in the grower (418) and finisher phase (441) versus control birds (389 grower and 415 finisher). These results suggested that both YCW fractions prepared from Saccharomyces cerevisiae can improve broiler performance when added at either a constant rate (250 ppm) or at a decreasing rate from 500 ppm for the starter to 125 ppm for the finisher phase.