Passage and digestibility of lucerne (Medicago sativa) hay in Japanese sika deer (Cervus nippon) and sheep under restricted feeding.

The mean retention time (MRT) of stained hay through the whole digestive tract and its digestibility were measured in Japanese sika deer (Cervus nippon) and were compared with those in sheep when lucerne (Medicago sativa) hay was fed at 10, 20 and 30 g/kg body-weight. The recoveries in faeces of plastic particles with five specific gravities were also measured in deer. MRT for deer was significantly shorter than that for sheep at 10 and 20 g/kg feeding levels. The digestibilities of dry matter, organic matter, and neutral-detergent fibre were significantly lower for deer than for sheep at 30, 30 and 10 g/kg feeding levels respectively. The recovery rates of plastic particles were increased, but the ruminated rates were decreased, with increasing specific gravity in deer. These results suggest that the lower digestibility of lucerne hay in Japanese deer may be due to a shorter MRT compared with sheep.