GROWTH, VOLUNTARY FOOD-INTAKE AND DIGESTION IN FARMED TEMPERATE AND TROPICAL DEER

Growth and voluntary feed intake (VFI) in grazing temperate farmed dee r species are influenced by the feeding value of the forage and the st age of the deer's seasonal cycle. Liveweight gain (LWG) of growing red deer was greater when perennial ryegrass (0.80)/white clover (0.20) p asture was grazed at 10 cm than 5 cm surface height, but venison produ ction by one year of age was still low. Chicory and red clover were of superior feeding value for deer than perennial ryegrass-based pasture s, increasing LWG of young red and hybrid (0.25 elk; 0.75 red deer) de er during summer and autumn, due to higher VFI and to higher organic m atter digestibility. Relative to perennial ryegrass, chicory disintegr ated faster in the rumen, with very low rumination time and faster rum en outflow rates of liquid and particulate matter. Inputs of red clove r and chicory substantially increased venison carcass weights at one y ear of age from grazing red and hybrid stags. In indoor pen feeding st udies, red deer were shown to have a seasonal cycle of digestive funct ion, with greater rumen mean retention time (MRT) and greater rates of rumen ammonia production in summer than in winter. It was deduced tha t the purpose of the digestive cycle was to maintain apparent digestib ility constant as VFI increased during summer. Tropical sambar deer we re also shown to have seasonal cycles in growth and VFI that were of r educed amplitude compared with red deer. Peak VFI and growth occurred in autumn and minimum VFI and growth occurred in spring. Feed conversi on (kg DM eaten/kg LWG) was more efficient for sambar than for red dee r, due to lower VFI and lower heat production, but there was no differ ence between species in digestive efficiency.