The Effect of Feeding Horses a High Fiber Diet With or Without Exogenous Fibrolytic Enzymes Supplementation on Nutrient Digestion, Blood Chemistry, Fecal Coliform Count, and In Vitro Fecal Fermentation

Sixteen Quarter Horse mares (450 to 500-kg body weight) were used in a complete randomized design to determine the effects of feeding a high fiber diet with or without exogenous fibrolytic enzymes on nutrient digestion, blood chemistry, fecal coliform count, and in vitro fecal fermentation. The treatments comprised feeding the horses (1) a basal diet without enzyme addition (control); (2) control diet plus cellulase at 10 mL/mare/d (CELL); (3) control diet plus xylanase at 10 mL/mare/d (XYL); or (4) control diet plus a mixture of 5 mL cellulase and 5 mL xylanase/mare/d (CX). The basal concentrate diet consisted of a mixture of 50% commercial concentrate and 50% wheat bran fed at 4 kg/horse, offered twice daily at 04:00 and 16:00 hours, and oat straw offered ad libitum at 05:00 and 17:00 hours. The enzyme allocation for each day was mixed with 1 kg of concentrate diet at 04:00 hours, and the experiment lasted for 15 days comprising 10 days of adaptation and 5 days for sample collection. The in vitro cecal fermentation with addition of 2 mu Lig dry matter (DM) of each enzyme (CELL, XYL, and CX) to a basal diet of oat straw and concentrates mixture (1:1 DM) as a substrate was carried out. The mares fed enzyme-supplemented diets had greater (P < .01) oat straw and total nutrients intakes compared with the control diet. Feeding enzyme-supplemented diets increased total nutrients digestibility (P < .05) and blood total protein (P = .0277) compared with the control. Feeding XYL-supplemented diet increased blood alanine transaminase and aspartate aminotransferase concentrations (P < .05) compared with control treatment. Lower fecal coliform count was obtained (P = .0114) with mares fed CX diet compared with control mares. The XYL and CX treatments had decreased asymptotic gas production (GP) (P = .0173) with lower rate of GP (P = .0412) compared with CELL treatment. CELL and XYL treatments had decreased (P = .0394) lag times compared with control and CX treatments. At 24 hours of incubation, CELL and XYL treatments decreased methane production (P = .0131), whereas CX treatment increased its production at 48 hours (P = .0202) compared with control treatment. No effect was observed (P > .05) with enzymes addition on carbon dioxide production at different hours of incubation compared with control treatment. Higher in vitro DM degradability values (P = .0092) were obtained with the enzyme CX treatment and increased with CELL treatment compared with the control and XYL, showing a greater pH with CELL than the other treatments. It can be concluded that addition of fibrolytic enzymes at 10 mL/mare/d improved feed intake and nutrients digestibility without affecting mare's health. (C) 2015 Elsevier Inc. All rights reserved.