RUMEN DIGESTION AND RUMEN OUTFLOW RATE IN DEER FED FRESH CHICORY (CICHORIUM-INTYBUS) OR PERENNIAL RYEGRASS (LOLIUM-PERENNE)

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 hourly at 2.25 kg dry matter (DM)/day to eight hand-re ared, rumen-fistulated castrated red deer stags kept in metabolism cra tes during December 1994 and January 1995 (summer). Apparent digestibi lity, rumen fractional disappearance rate (FDPR), rumen fractional deg radation rate (FDR), rumen fractional outflow rate (FOR) and mean rete ntion time (MRT) were measured. The ratio of readily fermentable carbo hydrate to structural carbohydrate was approximately three times highe r in chicory than in perennial ryegrass. Apparent digestibility of DM was higher in deer fed chicory than in deer fed perennial ryegrass (0. 785 v. 0.727), whilst apparent digestibility of neutral detergent fibr e (NDF) was lower in deer fed chicory (0.679 v. 0.755), due to a reduc ed hemicellulose digestibility (0.667 v. 0.783). Relative to deer fed perennial ryegrass, those fed chicory had higher rumen FDPR values for DM (14.5 v. 8.6 %/h), soluble carbohydrate (69.9 v. 54.7 %/h), cellul ose (15.5 v. 9.8 %/h) and lignin (6.8 v. 3.8 %/h). Rumen FDR in deer f ed chicory was higher than those fed perennial ryegrass for cellulose (11.4 v. 7.0 %/h) and lignin (2.7 v. 1.0 %/h), but tended to be lower for hemicellulose. Rumen FOR was higher and MRT was lower for both liq uid and particulate matter in deer fed chicory compared to deer fed pe rennial ryegrass. It is concluded that rumen FDPR and apparent digesti bility were much higher in deer fed chicory than in deer fed perennial ryegrass, due to faster degradation rates of most constituents in the rumen and faster outflow rates from the rumen. An exception was hemic ellulose, where reduced rumen degradation rates and shorter rumen part iculate MRT contributed to reduced apparent digestibility. Faster clea rance from the rumen, due to both faster degradation and outflow rates may be used to explain the greater voluntary feed intake (VFI), as we ll as faster growth rate in deer grazing chicory compared to those gra zing perennial ryegrass. Faster rates of lignin solubility in the rume n probably contributed to the more rapid breakdown of chicory in the r umen.