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

Abstract

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) and 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 β-glucanase activity. Normal diets were found to contain approximately 30 g/kg total β-glucan while the HAG and waxy diets contained approximately 40 g/kg total β-glucan. Soluble β-glucan was found to account for approximately 48%, 36% and 49% of the total β-glucan content of the normal, HAG and waxy diets, respectively. Generally birds fed the normal 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 weights and feed intakes, improved feed conversion ratios (g feed/g weight gain) and increased total (16% increase on average) and (HDL-cholesterol) concentrations in comparison to birds provided diets without enzyme. The ileal digesta dry matter content was increased by enzyme supplementation. Ileal digestibility 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 starch 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 β-glucan was also improved by enzyme supplementation and it was concluded that the β-glucanase used in this study may have reduced β-glucan-enhanced intestinal viscosity or nutrient encapsulation due to the presence of intact cell walls and thus, facilitated nutrient uptake. The ileal digestibility of starch was significantly lower among chickens fed the waxy diet without enzyme in comparison to animals fed the normal diet without enzyme but the difference was small. This difference was attributed to the effect of β-glucan when comparisons of starch digestibility between animals fed the waxy and normal diets with enzyme supplementation were made, no significant differences were observed.