125 Quantification of chewing frequency in horses consuming bermudagrass hay compared with other popular equine forages

Abstract

Bermudagrass is the most common fine-stemmed hay forage in the southeastern United State due to its adaptation to this region. The low cost and easy access contribute to bermudagrass hay being commonly fed, consequently it is detected in the digestive tracts of most horses submitted to regional veterinary clinics for impaction colic surgery. A potential association between fine stemmed forages and increased risk of impaction colic may be differences in chewing patterns compared with other hay types. Chewing encourages saliva production which assists in particle size reduction and works as a lubricant, assisting in transit through the gastrointestinal tract. Using 2 studies, the objective of this research was to compare the chewing rate of bermudagrass to other common equine forages. A preliminary 5-week study utilizing 5 privately owned horses routinely fed bermudagrass hay at one feeding and timothy hay at another was conducted to evaluate potential effects of hay type on chewing frequency. Horses were fitted with a RumiWatch® halter (ITIN + HOCH, Switzerland) to quantify chewing patterns and fed their normal amount of hay each feeding. Chewing patterns were continuously monitored until the next meal, and data was reported on a per minute basis. Hay was weighed before feeding, and refused hay was weighed back so the total chews/kg consumed could be calculated. Data were statisticallyanalyzed (Minitab v.21, State College, PA) as a mixed ANOVA with treatment as a fixed effect. Results indicate that horses chewed bermudagrass at a lower frequency compared with timothy (4643 vs. 7461 chews/kg, P = 0.003). At the conclusion of this study, a larger study utilizing 8 horses fed twice daily at 1.5% body weight in forage was conducted to test chewing frequency when eating bermudagrass, alfalfa, ryegrass, and orchardgrass hays. Horses received treatments in a 4 × 4 Latin square design having an acclimation period one week before a 3-d data collection using the RumiWatch® halter. Data were calculated as chews/kg and statistically compared using the same protocol used in the preliminary study. Results indicate that horses chew bermudagrass hay (3649 chews/kg) less as compared orchardgrass (4811 chews/kg), alfalfa (4571 chews/kg), and ryegrass (4763 chews/kg)(P < 0.001). Results further indicate no difference between the minutes chewed for bermudagrass (65.1 min/kg) to alfalfa (73.4 min/kg). However, there are differences between bermudagrass to orchardgrass (76.6 min/kg) and ryegrass (78.7 min/kg P < 0.05) which potentially causes reduction in saliva production and increased risk of impaction colic.