Assessing effects of yeast cell wall supplementation on threonine requirements in broilers as measured by performance...

The objective of this study was to evaluate whether or not the use of a prebiotic yeast cell wall (YCW) affects threonine requirements in starter broilers. Two hundred and forty 1-d-old Ross 308 broiler chickens were distributed among 2 Petersime battery brooder units (48 pens; 5 birds per pen). Different threonine to lysine ratios (0.60, 0.65, and 0.70 to 1.0) with 1.22% available lysine with and without YCW at 250 ppm was fed to the chickens in order to evaluate performance and intestinal morphology over a 21-d trial. A basal diet with 22% protein and 2,980 kcal/kg ME was prepared to create the 6 dietary treatments. The calculated lysine concentration was 1.34%, whereas threonine was 0.81, 0.88, and 0.94%, respectively. Pen weights and feed consumption were recorded at d 1, 7, 14, and 21 of the experiment. Jejunal and ileal samples were collected on d 21 for histology analysis to evaluate villi height (VH), crypt depth, villi width (VW), and muscularis thickness. A threonine to lysine ratio of 0.7:1.0 resulted in significant improvement of performance variables with increased jejunum VW and ileum VH compared with the other threonine to lysine ratios. Adding YCW to starter broiler did not affect the requirement for threonine.