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

Objective Overview

• This study investigated how horses chew bermudagrass hay compared to other common hay types and found that horses chew bermudagrass less per unit of weight, which may relate to digestive issues.

Introduction and Background

• Bermudagrass (Cynodon dactylon L.) is widely used as forage in the southeastern United States.
• Some controversy exists around feeding bermudagrass to horses because it has been linked with impaction colic, a serious digestive disorder.
• One hypothesis is that reduced fiber digestibility in bermudagrass may contribute to these digestive problems.
• However, differences in how horses masticate (chew) bermudagrass, particularly fine-stemmed varieties, had not been thoroughly studied before this research.
• This study aims to characterize how horses chew bermudagrass relative to other hays to better understand potential impacts on digestion.

Methods

• The research consisted of two parts: a preliminary study and a main study.
• Preliminary study:
  • Five sport horse warmblood geldings, averaging 16.4 years old and 534 kg, routinely fed bermudagrass and timothy hay, were observed for chewing activity.
• Main study:
  • Eight horses (5 mares, 3 geldings), primarily Quarter horses or crosses, aged about 5.5 years and 495 kg were used.
  • Horses were fed four types of hay: bermudagrass, alfalfa, annual ryegrass, and orchardgrass in a randomized block design.
  • Each horse received 1.5% of their body weight in hay daily (as fed basis).
  • Chewing activity was recorded using the EquiWatch® automated halter-based sensor system, allowing objective measurement of mastication.

Results

• Horses consumed significantly fewer chews per kilogram of bermudagrass hay compared to timothy, orchardgrass, alfalfa, and annual ryegrass hays (statistical significance at P<0.0001).
• This means that for the same weight of hay, horses masticated bermudagrass less than the other types.
• The reduced chewing could lead to larger particle sizes entering the digestive tract, which may affect fiber breakdown and digestibility.

Conclusions and Implications

• Consumption of bermudagrass hay results in reduced mastication activity in horses.
• Less chewing may contribute to poorer fiber breakdown and could be a factor in digestive disturbances such as impaction colic associated with bermudagrass.
• The study highlights the need for further research to explore the connection between chewing behavior, fiber digestibility, and colic risk.
• It supports the idea that chew characteristics should be considered when evaluating and recommending forage types in equine diets.