Original ResearchThe 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
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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