RATE OF PASSAGE OF BARLEY DIETS WITH CHROMIUM-OXIDE - INFLUENCE OF AGE AND POULTRY STRAIN AND EFFECT OF BETA-GLUCANASE SUPPLEMENTATION

Three-week-old broiler chicks and 1-yr-old Leghorn cocks were used to determine the effect of beta-glucanase addition (experimental product from Trichoderma longibrachiatum) to a 60% barley-based diet on rate of feed passage, transit time, and mean retention time. Fecal chromium oxide content was used to calculate cumulated and noncumulated excretion data. A Hill equation was chosen to test the goodness of fit of cumulative excretion curves. Time of 50% (T50) and 1% (T1) chromium excretion, calculated from cumulative excretion curves, were affected by beta-glucanase addition, but this effect also was influenced by age or strain. In broiler chicks, T50 (P <.02) and T1 (P <.06) decreased with beta-glucanase addition. In cocks, T50 (P <.04) and T1 (P <.05) increased with beta-glucanase addition. Noncumulative excretion data yielded similar results. In the absence of beta-glucanase, peak chromium excretion occurred 1 h later in broiler chicks than in cocks. These differences in feed passage rate may explain why intestinal viscosity caused by the presence of beta-glucan did not act in the same manner in broiler chicks as in cocks. When beta-glucanase was added, the age-related difference was removed and rates become similar. In broiler chicks, the rate of feed passage is related to feed intake. Thus, this could explain the different effects in terms of feed utilization.