In Vitro Assessment of Fecal Inocula From Horses Fed on High-Fiber Diets With Fibrolytic Enzymes Addition on Gas, Methane and Carbon Dioxide Productions As Indicators of Hindgut Activity

Abstract

This study was aimed to assess the effect of fecal inocula from horses fed on concentrate (restricted amount daily) and oat straw (ad libitum) supplemented with fibrolytic enzymes on in vitro hindgut activity. Cellulase (CE), xylanase (XY) and CE+XY (1:1 v/v; CX) were tested at three levels (μL/g DM): 0, 1 and 3, in addition to control without enzyme addition (EP0). Fecal inocula were collected from 16 Quarter Horse mares supplemented with enzyme at 0 (FCOwithout enzyme), or fed 10 ml enzyme/mare/day of CE (FCE), XY (FXY) or CE+XY (1:1 v/v; FCX) for 15 days. The fecal content mixed with the culture media were used for incubation in bottles containing 1 g DM of substrate (a mixture of concentrate and oat straw (1:1 DM)). Gas (GP), methane (CH4) and carbon dioxide (CO2) productions were measured at 2, 4, 6, 8, 10, 12, 24 and 48 h post-incubation. Interactions occurred (P˂0.05) between fecal type × enzyme product for the asymptotic GP, the rate of GP, CH4 production, and fermentation kinetic parameters. Moreover, interactions were observed (P˂0.05) between fecal type × enzyme product × enzyme dose for the rate of GP, CH4 production and DM digestibility. Xylanase at 3 μL/g DM with FXY fecal increased (P˂0.05) the asymptotic GP and calculated fermentation parameters. At 24 h and 48 h and without enzyme, FCX and FXY, respectively, had the highest (P˂0.05) CH4 production. It can be concluded that xylanase enzyme at 3 μL/g DM was the most effective compared to other treatments.