Nutritional influence of broiler chicken diets based on covered normal, waxy and high amylose barleys with or without enzyme supplementation

A total of 384 day-old broiler chickens were fed unpelleted diets based on covered barley cultivars (696 g/kg) with normal (Golf) high amylose (HAG) a nd high amylopectin (waxy) starch for a total of 18 days. Diets were fed ad libitum without or with supplementation of a commercial enzyme preparation containing beta-glucanase activity. Normal diets were found to contain app roximately 30 g/kg total beta-glucan while the HAG and waxy diets contained approximately 40 g/kg total beta-glucan. Soluble beta-glucan was found to account for approximately 48%, 36% and 49% of the total beta-glucan content of the normal, HAG and waxy diets, respectively. Generally birds fed the n ormal diets weighed more, consumed more feed and had lower feed conversion ratios than animals fed the HAG and waxy diets, respectively, at 13 days of age. Enzyme supplementation of diets generally increased chicken body weig hts and feed intakes, improved feed conversion ratios (g feed/g weight gain ) and increased total (16% increase on average) and (HDL-cholesterol) conce ntrations in comparison to birds provided diets without enzyme. The ileal d igesta dry matter content was increased by enzyme supplementation. Ileal di gestibility of nutrients was generally improved among chickens given enzyme supplemented diets when compared to animals fed diets without enzyme, the greatest increase in ileal fat digestibility (19% increase) and ileal starc h digestibility (9% increase) being observed among animals given the enzyme supplemented waxy diet in comparison to the unsupplemented waxy diet. The ileal digestibility of total beta-glucan was also improved by enzyme supple mentation and it was concluded that the beta-glucanase used in this study m ay have reduced beta-glucan-enhanced intestinal viscosity or nutrient encap sulation due to the presence of intact cell walls and thus, facilitated nut rient uptake. The ileal digestibility of starch was significantly lower amo ng chickens fed the waxy diet without enzyme in comparison to animals fed t he normal diet without enzyme but the difference was small. This difference was attributed to the effect of beta-glucan when comparisons of starch dig estibility between animals fed the waxy and normal diets with enzyme supple mentation were made, no significant differences were observed. (C) 1999 Els evier Science B.V. All rights reserved.