Mastication characterization of horses fed bermudagrass hay in a two-part field study.

BACKGROUND Bermudagrass (Cynodon dactylon L.) is a common forage in the southeastern United States but remains controversial in equine diets due to reported associations with impaction colic. Reduced fiber digestibility has been proposed as a contributing factor, however differences in mastication of fine-stemmed bermudagrass hay have not been studied and may play a role in digestive disturbances.

AIMS/OBJECTIVES To compare chewing characteristics, including chews per unit weight and chews per minute, in horses consuming bermudagrass hay compared to other common hay types.

METHODS Two studies were conducted. In the preliminary study, five sport horse warmblood geldings (ages 16.4 ± 6.4 years, 534 ± 50 kg) routinely fed bermudagrass and timothy (Phleum pratense L.) hays were monitored for chewing activity. In the main study, eight horses (ages 5.5 ± 1 years, 5 mares, 3 geldings, 494.8 ± 29.8 kg, Quarter horse or Quarter horse cross) were fed bermudagrass, alfalfa (Medicago sativa L.), annual ryegrass (Lolium multiflorum Lam.), and orchardgrass (Dactylis glomerata L.) hay in a randomized block design at 1.5% of body weight (BW) as fed daily. Chewing activity was recorded using the EquiWatch® automated halter-based sensor.

RESULTS Horses took fewer chews per kg when consuming bermudagrass compared to timothy, orchardgrass, alfalfa, and annual ryegrass (P<0.0001).

CONCLUSION Consumption of bermudagrass hay led to reduced mastication in horses, and further investigation into this relationship with digestive disturbances is warranted.