Chewing behaviour in the domestic donkey (Equus asinus) fed fibrous forage

A study was conducted to investigate chewing activity in domestic donkeys eating long-stem, high-fiber forage. Five donkeys (body weight 198±15 kg) were fed 2 types of forage containing equal amounts of fiber (65% neutral detergent fiber: NDF) at two levels of crude protein (CP). Forage consumed was either a mixed legume/orchard grass hay (CP 13.7%) or a grass hay (CP 6.5%). Chewing rate (chews/min) and rate of feed consumption (min/kg of dry matter (DM) or of NDF) were determined by direct observation. The study was designed as a two-period cross-over design with 3 sets of observations per animal per diet. There was no significant effect of protein level or forage type on average chewing rate (53±2 chews/min), time to consume 1 kg of DM (120±12 min) or 1 kg of NDF (184±18 min). Chewing rate was no different at the start vs. end of a 1-h meal for animals eating mixed legume/grass hay, but was significantly (P<0.05) slower later in the meal for donkeys eating grass hay. Each gram of NDF was chewed approximately 10 times. Donkeys consumed fiber at a faster rate than has been reported for equal or greater-sized ruminants, even though they did not chew at a faster speed. This behaviour could be due to a more efficient tooth and jaw apparatus, the swallowing of larger feed particles, or a combination of factors, and supports the postulated high intake feeding strategy of the donkey. Some donkeys may be prone to consume food, even forage, especially fast, without sufficient chewing, and may therefore be liable to esophageal obstruction.