Effect of different amylases on the utilization of cornstarch in broiler chickens
This study compared the effect of different amylases on the utilization of cornstarch in broiler chickens fed a corn-based diet. Three-day-old Arbor Acres plus male chickens were randomly divided into 7 treatments and fed a diet supplemented with different sources and concentrations of amylase: 1,500 U/kg and 3,000 U/kg α-1,4 amylase from Aspergillus oryzae (α-amylase A); 480 U/kg and 960 U/kg α-1,4 amylase from Bacillus subtilis (α-amylase B); 200 U/kg and 400 U/kg α-1,6 isoamylase from B. subtilis; and the control. The experimental period comprised 11 d, during which performance, nutrient digestibility, digestive enzyme activity, intestinal morphology, and glucose transporter transcription of the chickens were evaluated. The results indicated that 1,500 U/kg α-amylase improved the digestibility of energy and decreased the feed conversion rate compared to α-1,6 isoamylase (P < 0.05). Supplemental 400 U/kg α-1,6 isoamylase decreased ileal digestibility of amylopectin and total starch (P < 0.05) compared to 200 U/kg α-1,6 isoamylase, α-amylase A, α-amylase B, and the control (P < 0.05). Supplemental α-1,6 isoamylase decreased (P < 0.05) insulin content. Supplemental 3,000 U/kg α-amylase A and α-1,6 isoamylase increased (P < 0.05) the relative weight of the liver. In addition, 3,000 U/kg α-amylase A, 480 U/kg α-amylase B, and α-1,6 isoamylase decreased the V:C in the duodenum and ileum. α-amylase A increased sucrase activity in the jejunum (P < 0.05), whereas 400 U/kg α-1,6 isoamylase reduced maltase activity in the duodenum (P < 0.05). Furthermore, 3,000 U/kg α-amylase A and α-amylase B decreased (P < 0.05) sodium/glucose cotransporter 1 (SGLT1) mRNA expression in the duodenum and jejunum. However, 200 U/kg α-1,6 isoamylase increased glucose transporter 2 (GLUCT2) in the duodenum (P < 0.05). These results suggest that exogenous amylase affects the digestibility of starch by affecting disaccharidase activity in the intestine, nutrient requirements for intestinal maintenance by the V:C, and nutrient absorption and metabolism via GLU transporter mRNA expression. Different sources and concentrations of amylases had varying effects on broilers.