Tn. Barry et al., GROWTH, VOLUNTARY FOOD-INTAKE AND DIGESTION IN FARMED TEMPERATE AND TROPICAL DEER, Acta veterinaria Hungarica, 46(3), 1998, pp. 369-380
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.