Resumen:
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.