INTRARUMINAL PARTICLE-SIZE REDUCTION IN DEER FED FRESH PERENNIAL RYEGRASS (LOLIUM-PERENNE) OR CHICORY (CICHORIUM-INTYBUS)

Pure swards of chicory (Cichorium intybus) and perennial ryegrass (Lol ium perenne) were grown at Palmerston North, New Zealand. They were cu t daily and fed fresh at 2 kg dry matter (DM)/day to ten hand-reared r umen fistulated castrated red deer stags kept in metabolism crates in April and October 1994. The efficiency of particle breakdown during th e time allowed for rumination ([C.PART]) to below the critical size re quired to leave the rumen (passage through a 1 mm sieve) and jaw activ ities (i.e. eating and ruminating) were measured. Total eating time an d the number of eating bouts were similar for deer fed each forage, bu t deer fed chicory had a greater chewing rate during eating (97.4 v. 8 1.0 chews/min), and a higher number of chews/g DM eaten (36.2 v. 31.5) . Deer fed chicory had lower total ruminating time (30 v. 257 min/22.5 h), lower number of boli ruminated (38 v. 440/22.5 h), lower number o f rumination bouts (5.4 v. 16.2/22.5 h) and less chews per minute rumi nating (16.5 v. 44.3) than those fed perennial ryegrass. Of the ten de er used to measure ([C.PART]), only four ruminated when fed chicory co mpared with nine when fed perennial ryegrass. Deer fed chicory had a h igher efficiency of particle breakdown ([C.PART]; 0.64 v. 0.42), highe r fractional degradation of particles > 1 mm (9.2 v. 5.1%/h) and faste r fractional disappearance of total DM from the rumen (10.2 v. 5.3%/h) . All three measurements for chicory were similar in deer that did or did not ruminate, but with perennial ryegrass, all values were conside rably reduced in the deer that did not ruminate. It was concluded that chicory can be broken down faster in the rumen, with less rumination being required than for perennial ryegrass, and that some deer (60%) c ould break down swallowed chicory to below the critical particle size without ruminating at all. The faster clearance of DM from the rumen e xplains the high voluntary feed intake (VFI) of deer grazing chicory. Future research needs to be done to partition rumen fractional disappe arance rate into its components, rumen fractional degradation rate and rumen fractional outflow rate in deer fed chicory and perennial ryegr ass.