Effect of application rate of a fibrolytic enzyme product on in vitro ruminal fermentation of three low-quality substrates

Abstract

1 página.-- Trabajo presentado al Joint Meeting of the ADSA-PSA-AMPA-CSAS-ASAS (Phoenix, Arizona, Estados Unidos, del 15 al 19 de Julio, 2012).The effects of a fibrolytic enzyme product (Dyadic Xylanase PLUS, Dyadic Inc. USA) on the in vitro ruminal fermentation of 3 low-quality forages (rice straw, corn stover and grass hay) were investigated using batch cultures of mixed ruminal microorganisms. Five different treatments were tested: 0X (control), 0.5X, 1X, 4X and 10X (where 1X was the manufacturer recommended dose, 20 mg/g DM). Enzymes were applied directly onto the forages 24 h before incubation with buffered ruminal fluid at 39°C for 9 h. Four incubation runs were performed on different days. Gas production was measured at 3, 6, 9 h, and the main fermentation parameters were determined at the end of the incubation. Five concentrations of enzyme, 3 substrates, and the interaction of enzyme x substrate were included in the model as fixed effects, whereas incubation day was considered as a random effect. There were enzyme x substrate interactions for all the parameters measured, indicating different effects on each feed. All doses of enzyme product increased (P < 0.05) gas production after 3, 6 and 9 h of incubation for corn stover and grass hay, whereas only 10X increased (P < 0.05) gas production at 3 and 6 h for rice straw, compared with the control. All doses stimulated (P < 0.05) gas production after 9 h of incubation for the 3 substrates. Dry matter disappearance increased (P < 0.05) with doses 4X and 10X for the 3 substrates. Doses 0.5X, 1X and 4X decreased (P < 0.05) NH3 concentrations for the 3 substrates, but 10X had no effect (P > 0.05). Enzyme treatment increased (P < 0.05) total VFA production to 116, 120, 131 and 177% of control values for 0.5X, 1X, 4X and 10X, respectively, for grass hay, to 147, 173, 190 and 268% of control values for corn stover, and 125, 149, 160 and 282% of control values for rice straw. Acetate:propionate ratio decreased (P < 0.05) in grass hay and maize stover treated with any dose of the enzyme product, but in the case of rice straw, 0.5X, 1X and 4X doses increased (P < 0.05) this ratio and 10X decreased (P < 0.05) it, compared with the control. The results indicate that the pre-treatment of these low-quality forages with a wide range of doses of the fibrolytic enzyme has a positive effect on ruminal fermentation and the enzyme product is a good candidate to improve their digestibility.Peer reviewe