Venison production from weaner Red Deer (Cervus elaphus) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in the Department of Animal Science, Faculty of Agricultural and Horticultural Sciences, Massey University, Palmerston North, New Zealand
Forty four weaner red deer (Cervus elaphus) fawns (26 stags; 18 hinds) were used to investigate the effects of grazing pure red clover (Trifolium pratense) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pastures and immunisation against melatonin upon growth and venison production, with the objective of the stags attaining a minimum target slaughter liveweight (92 kg LW;>50 kg carcass) by 12 month of age. The experiment was conducted at the Deer Unit Massey University, NZ, during 1991. The animals were randomly allocated into eight treatment groups (starting on 13 March 1991), with the combination of pasture types ((pure red clover (RC) or perennial ryegrass/white clover (PRG/WC), sex (male or female) and immunisation (against melatonin or placebo only). The deer were rotationally grazed on either RC or PRG/WC pasture (feed allowances 6, 7 kg DM/h/day, respectively) during autumn and spring. During winter, all animals were combined and grazed together on PRG/WC pasture (6 kg DM/h/day feed allowance), at a pasture residual DM of 1100 kg DM/ha. The subcutaneous anti-melatonin injections were administered to the immunisation groups at birth and at weaning. Pre-grazing herbage mass for RC or PRG/WC were respectively 3568, 3706 kg DM/ha in autumn; 2726, 2150 kg DM/ha in spring; 1736 kg DM/ha in winter. Post-grazing herbage mass for RC or PRG/WC averaged at 1822, 1882, in autumn; 1705, 1334, in spring; and 1170 kg DM/ha in winter, respectively. Total nitrogen (N) and organic matter digestibility (OMD) concentration of both feed on offer (FO) and diet selected (DS) were higher in RC than PRG/WC (FO total N: 3.4 vs 3.4% DM in autumn, 4.1 vs 2.6% DM in spring; FO OMD: 77.3 vs 78.6% OM in autumn, 84.5 vs 80.3% OM in spring; DS total N: 4.2 vs 3.9 % DM in autumn, 4.7 vs 3.3% DM in spring; DS OMD: 84.2 vs 83.2% OM in autumn, 87.7 vs 82.4% OM in spring). Liveweight gain (LWG) of RC stags and hinds was significantly higher than PRG/WC animals in autumn (237 vs 207; 197 vs 159 g/d; P<0.01) and in spring (346 vs 281; and 260 vs 188 g/d; P<0.001), but not in winter (94 vs 95; 38 vs 40 g/d; P>0.05). Weaner stags and hinds grazing RC forage had significantly higher voluntary feed intake (VFI) than the comparable animals grazing PRG/WC pasture in either autumn (P<0.05) or spring (P<0.001). By 12-month of age, stags grazing RC were 6 kg heavier and hinds 7 kg heavier than animals grazing PRG/WC forage. All (100%) RC stags attained the minimum target slaughter LW (>92 kg LW; 50 kg carcass) by 12-month of age at the end of November, compared to 90% of PRG/WC stags. Carcass weights (kg) and dressing percentage (%) of RC stags were significantly higher than PRG/WC stags (58.9 vs 53.3 kg, P<0.01; 56.2 vs 52.4%, P<0.001), but the carcass GR was not different (P>0.05) either after or before being adjusted to equal carcass weight. The immunisation treatment did not provide any significant responses (P>0.05) in LWG and did not affect plasma prolactin concentrations. The immunisation against melatonin treatment did not give any significant effects (P>0.05) on all measurements of carcass production. In conclusion, these studies show that early venison production from grazed PRG/WC pastures is possible, and that this can be further improved by inputs of RC. Weaner red deer grazing red clover forage during autumn and spring grew and produced venison better than animals grazing conventional PRG/WC pastures. The immunisation against melatonin did not provide any significant effects on growth and venison production from weaner red deer grazing either RC or PRG/WC forages. RC offers very good potential as a special purpose forage for venison production.