EFFECTS OF HULLESS BARLEY AND EXOGENOUS BETA-GLUCANASE LEVELS ON BETA-GLUCAN DEPOLYMERIZATION, DIGESTIVE TRACT PHYSIOLOGY AND MORPHOLOGY, AND PERFORMANCE IN CHICKENS

Abstract

The reduced use of antibiotics in poultry feed has led to increase enteric disease, and investigation of alternatives to antibiotics has become a major concern. The study evaluated effects of hulless barley (HB) and β-glucanase (BGase) on β-glucan depolymerization, performance, and digestive tract characteristics of chickens. Two broiler trials (a battery cage trial and a floor trial/ coccidiosis challenged birds) and a laying hen trial were conducted by feeding the birds with graded levels of high β-glucan HB and BGase. Exogenous BGase depolymerized high MW β-glucan in the ileum of cage-raised broilers. However, few or no treatment effects noted for digestive tract characteristics and performance. In coccidiosis challenged broilers, BGase depolymerized high MW β-glucan in HB in a dose-dependent manner but had minor effects on digestive tract characteristics. Hulless barley reduced broiler performance and BGase alleviated the effects. However, in young birds fed highest levels of HB and BGase did not affect weight gain while increasing feed efficiency. Overall, HB increased digestive tract size and content, whereas BGase decreased them. In laying hens, BGase depolymerized high MW β-glucan in the ileum in a dose-dependent manner. Effects of medication and BGase were evaluated on broilers fed HB-based diets. Both BGase and medication depolymerized high MW β-glucan in the ileum. Medication and BGase increased the performance in coccidiosis challenged broilers. Effects of HB and BGase were also tested on Salmonella colonization in broilers challenged with Salmonella Enteritidis. Hulless barley decreased Salmonella counts in cloacal swabs and the spleen up to d 1 after the Salmonella challenge whereas, increased the counts in spleen after d 1 of the challenge in broiler chickens. However, BGase did not affect Salmonella colonization. In conclusion, BGase depolymerized ileal soluble high MW β-glucan in HB in a dose-dependent manner. The resulting low MW β-glucan increased performance in older birds, although no improvement or a reduction of performance was observed in young broilers. The effects of HB and BGase on digestive tract physiological measurements were minor and inconsistent across the experiments. It appears BGase can partially replace antibiotics in HB-based broiler diets.