Original Research
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

https://doi.org/10.1016/j.jevs.2015.07.009Get rights and content

Highlights

  • Addition of fibrolytic enzymes improved intake of oat straw by 67% to 83%.

  • Enzyme-supplemented diets increased all nutrients digestibility.

  • Cellulase and/or xylanase mixture decreased fecal shedding of Escherichia coli by 17%.

  • Enzyme treatment improved fecal gas production and dry matter degradability.

  • Xylanase diet increased blood alanine transaminase and aspartate aminotransferase.

Abstract

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 μL/g 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 treatments compared with control treatment. Fermentation pH was lower (P = .0396) with 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.

Introduction

Horses are free-ranging herbivores adapted to eating large amounts of high fiber diets for the normal function of the equine digestive system. However, pathologies such as gastric ulceration, laminitis, hindgut acidosis, and colic are associated with feeding diets high in cereal grain [1]. Therefore, there is increasing interest in feeding fiber-based diets with low levels of starch and sugar to meet the energy demands of the horse and reduce incidences of such disorders. Feeding horses a minimum of 1% of their body weights (BWs) as fibrous feedstuffs can minimize occurrence of colic, gastric ulcers, hindgut acidosis, and stereotypical behaviors [2].

Forage feeds have low protein content and low nutrients digestibility [3], [4]. There is a need for developing new feeding strategies to meet horse nutrient requirements while maintaining gut health and integrity. In ruminant diets, exogenous fibrolytic enzymes have been shown to improve the digestion of plant fiber fractions by improving ruminal fermentation working synergetically with endogenous rumen microbial enzymes [4]. The large intestine of the horse is a fermentation system similar to the rumen [5]. Microorganisms living in the rumen of ruminant animals and in the cecum of horses give them the ability to breakdown fibers by microbial fermentation to meet energy demands [6].

Numerous studies have been conducted with ruminants to investigate the potential benefits of exogenous fibrolytic enzyme supplementation in improving total tract nutrient digestibilities [7]. Supplementing the diet of horses with exogenous fibrolytic enzymes has gained substantial interest in recent years [6], [8]. However, the potential of exogenous enzymes to enhance the digestion of plant structural carbohydrates in the hindgut of the equine working in synergism with endogenous microorganisms is inconclusive [8]. Hainze et al [8] fed horses a diet of grass hay with textured concentrate, pelleted concentrate, whole oats, or alfalfa-lucerne (Medicago sativa) supplemented with cellulase and reported that cellulase administration improved the digestion of neutral detergent fiber (NDF) and acid detergent fiber (ADF) in the oats and textured feeds, but decreased the digestion of NDF and ADF in the alfalfa-lucerne. In contrast, Murray et al [9] reported a significant reduction in in vivo digestibility of the fibrous fractions of enzyme-treated high-temperature dried lucerne and ensiled lucerne. Similarly, O'Connor-Robison et al [6] fed Arabian geldings a hay-based diet supplemented with cellulase and noted that cellulase addition decreased digestion of the fiber components.

Therefore, the aim of the present study was to determine the effect of feeding cellulase, xylanase, and their mixture (1:1 vol/vol) on nutrient digestion, blood chemistry, fecal coliform count, and in vitro fecal fermentation in horses fed a high fiber-based diet.

Section snippets

Materials and Methods

All procedures involved in handling animals during the experimental period were conducted according to the official Mexican standard of animals care number NOM-051-ZOO-1995.

Feed Intake and Nutrient Digestibility

The mares fed enzyme-supplemented diets had greater (P < .01) oat straw and total nutrient intakes compared with the control diet. Moreover, feeding enzyme-supplemented diets increased total nutrients digestibility (P < .05) compared with the control diet. Mares fed CELL diet had the highest CP digestibility (P < .05) compared with mares fed other diets (Table 1).

Blood Chemistry and Fecal Coliform Count

Feeding enzymes increased blood total protein (P = .0277) compared with the control. Feeding XYL-supplemented diet increased blood

Feed Intake and Nutrient Digestibility

The intake of oat straw was higher by 67% to 83% with addition of enzymes. This may be partly due to the greater nutrients digestibility with enzyme supplementation, which is consistent with previous results [9]. However, O'Connor-Robison et al [6] did not find a feed intake effect with cellulase in horse diets. To our knowledge, there are no in vivo studies available on cecal fermentation in horses. Because the large intestine of the horse is a fermentation system similar to the rumen [5], our

Conclusions

Addition of fibrolytic enzyme of cellulase, xylanase, and their mixture (1:1 vol/vol) at 10 mL/animal/d resulted in greater intake of oat straw. Improved feed intake was coupled with increased nutrient digestibilities. Blood parameters were altered by the treatments with lower fecal shedding of E. coli of about 17% with the treatment of cellulase and/or xylanase mixture. In vitro fecal fermentation showed higher GP and DMD with enzyme treatment with the better results with cellulase addition at

Acknowledgments

The authors acknowledge the financial support from the IAEA, Vienna, Austria (Research Contract Number MEX16307 within the D3.10.27 Coordinated Research Project). Kholif, A.E. thanks the National Council for Science and Technology (CONACyT, Mexico) and The World Academy of Sciences (TWAS, Italy) to support his Postdoctoral fellowship at the Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México.

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