Effects of feruloyl esterase, non-starch polysaccharide degrading enzymes, phytase, and their combinations on in vitro degradation of rice bran and nutrient digestibility of rice bran based diets in adult cockerels

Abstract

The objective of this research was to evaluate the feasibility of improving the nutritive value of rice bran used as poultry feed ingredient by the combination of feruloyl esterase (FAE), non-starch polysaccharide degrading enzyme cocktail (non-starch polysaccharide enzyme containing xylanase, cellulase, and β-galactosidase, NSPase), and phytase. After analyzing the phenolic acid profile of defatted rice bran (DFRB), an in vitro degradation experiment, and an in vivo metabolism assay were conducted. The effects of FAE, NSPase, and phytase were assessed in a 2×2×2 factorial in vitro experiment using DFRB as substrate. Feruloyl esterase, NSPase, and their combination increased the release of ferulic acid from DFRB (P<0.001). Non-starch polysaccharide degrading enzyme cocktail increased reducing sugar production (P<0.001). Phytase addition increased the dry matter disappearance (P<0.001), but resulted in a reduction in the levels of ferulic acid and reducing sugar released when combined with FAE and NSPase, respectively. In in vivo experiment, 40 adult cockerels (BW=2.2±0.1kg) were randomly divided into 5 treatments with 8 individual cockerels per treatment. Cockerels in 1 treatment were force-fed 1 of full-fat rice bran based diets [without enzyme supplementation (RB), with NSPase (RBN), NSPase+FAE (RBNF), NSPase+phytase (RBNP), or NSPase+FAE+phytase (RBNFP) addition, respectively]. Enzyme additions improved the nutrient digestibility of rice bran. The greatest enhancements in digestibility coefficients of dry matter (P=0.036), gross energy (P<0.001), ether extract (P<0.001), and neutral detergent fiber (P=0.01) were found in the RBNF and RBNFP diets. The apparent metabolizable energy of full-fat rice bran based diets increased from 12.05 (RB diet) to 13.05 (RBNF diet), and, then, to 13.13MJ/kg (RBNFP diet). In conclusion, combining FAE with NSPase and phytase improved both in vitro dry matter degradation and ferulic acid release, and in vivo nutrient digestibility of rice bran based diets. It showed a high potential in improving the use of rice bran as poultry feed.