The forage intake and digestibility, and the chewmg behaviour of rasa deer (Cervus timorensis) and merino sheep were studied.
In Experiment 1, five dried forages - one legume (lucerne), one straw (barley) and three grasses (kikuyu, rhodes grass and spear grass), and two cereal grains (barley and sorghum) were subjected to an incubation medium containing rusa deer or sheep ramen fluid. The in vitro dry matter (DM) digestibilities (IVDMD), the potential degradabilities of insoluble DM, nitrogen (N) and neutral detergent fibre (NDF), and the rates of degradation of insoluble DM, N and NDF were investigated.
Comparisons between deer and sheep showed few differences in IVDMD for either individual forages or the pooled data over all forages. The IVDMD of barley grain tended to be greater when it was incubated in deer than in sheep ramen fluid. The potentially degradable insoluble DM and potentially degradable insoluble N (PDIN) of lucerne were greater (P<0.05) for deer than sheep, while the PDIN of barley straw was greater (P<0.05) for sheep than deer. The potentially degradable insoluble NDF (PDINDF) of barley straw was greater (P<0.05) for deer than sheep. The PDINDF of sorghum was greater (P<0.05) for sheep than deer. The degradation rates of insoluble DM, insoluble nitrogen and insoluble NDF were similar for sheep and deer, both for forages and cereal grains (P>0.05).
Chewing behaviours of rasa deer and merino sheep were observed in Experiment 2. Three rusa stags aged 18 months were housed together in a fenced pen, and five sheep aged 2-3 years were individually confined in metabolism cages. The animals were fed lucerne hay, rhodes grass hay, or barley straw. Lucerne hay was eaten more quickly (P<0.05) than rhodes grass or barley straw by both deer and sheep, and deer ate rhodes grass more quickly than barley straw. During eating, deer chewed lucerne hay faster than barley straw, but sheep chewed (chews/minute) all forages at similar rate. Both deer and sheep chewed lucerne hay more efficiently (fewer chews per g DM) than barley straw, and sheep also chewed this legume more efficiently than rhodes grass hay (P<0.05).
Rumination rate (chews/minute), time spent ruminating (second/bolus), rumination efficiency (chews/bolus), and regurgitation rate (second) were similar across all forages in both deer and sheep. It appeared from these experiments that sheep chewed all forages more quickly than deer, but deer seemed to chew low-quality forages (rhodes grass hay and barley straw) more efficiently (less chews/g DM eaten) than sheep. It also appeared that deer mminated forages more efficiently (chews/bolus) than sheep, and the elapsed time between regurgitation of consecutive boli was shorter for deer than sheep.
In Experiment 3, five rasa stags (mean live weight 77.5 ± 8.0 kg, mean ± SD), and seven merino wethers (41.6 ± 2.0 kg) were individually housed in metaboUsm pens and fed once daily with lucerne hay, rhodes grass hay or barley straw as sole diet constituents. DM and NDF intakes were similar for deer and sheep when they were fed with lucerne hay, but deer consumed more DM and NDF of rhodes grass hay or barley straw than sheep (P<0.05). Deer and sheep digested the DM of lucerne hay and barley straw with similar efficiencies but deer digested the DM of rhodes grass hay better than sheep. Deer were superior to sheep in digesting the NDF of lucerne hay and rhodes grass (P<0.05) and tended to digest the NDF of barley straw better than sheep. N balance was greater for deer than sheep when they were fed on lucerne hay.
The results of these experiments suggest that deer and sheep differ in their chewing behaviour. They respond in similar ways when fed on high-quality forages but deer eat more when fed on low-quality forages and are superior to sheep in digesting the cell wall of forages.
The differences between deer and sheep apparent in these experiments, indicate that it would be unwise to use sheep nutritive value data to predict the responses of deer to similar feedstuffs.