Abstract

An experiment was designed to assess the effects of graded levels of β-mannanase on performance, gut morphology and some blood proteins and leucocytes of broilers provided with diets based on corn and soybean meal. Broiler chickens are divided four group and supplied diet which contains 0, 500, 700, or 900 g/ton β-mannanase. Each treatment contained 4 pen with 15 birds/pen. 900 g/ton β-mannanase supplementation significantly reduced feed intake but did not influenced body weight gain and feed conversion ratio in both finisher and total period. 900 g/ton β-mannanase supplementation increased (P < 0.01) villus height and crypt depth and decreased (P < 0.01) goblet cell number, epithelial thickness and ratio of crypt depth to villus height in different sections of small intestine, suggesting that β-mannanase improves gut morphology in broiler chickens. The addition of β-mannanase at 700 and 900 g/ton to the diets significantly (P < 0.05)reduced jejunal viscosity compared with the control group. β-mannanase did not influence the blood serum proteins (albumin, alpha 1-, alpha 2-, beta and gamma-globulins) eosinophils and monocytes, but the addition β-mannanase increased lymphocyte, and decreased heterophil and heterophil: lymphocyte (H:L) ratio (p < 0.05). Thus it improved chickens immune system.

Key words: Broiler, leucocytes, viscosity, serum proteins.