Early venison production from red deer (Cervus elaphus) as affected by grazing perennial or annual ryegrass pastures, pasture surface height and immunization against melatonin

Abstract

S U M M A R YTwo grazing experiments in New Zealand, using newly weaned red deer stags, assessed methods of maximizing growth over winter and spring, with the objective of attaining a slaughter weight of 92 kg liveweight (> 50 kg carcass) at the end of spring, by 12 months of age. Perennial ryegrass/white clover pastures, and the same direct-drilled with an annual ryegrass, were grazed at two surface heights (5 cm and 10cm; Experiment 1; 1988) or at similar pasture mass (Experiment 2; 1989). Balanced groups of stags grazing each forage were immunized against melatonin, commencing at 3 months of age (Expt 1) or at birth (Expt 2). Moata annual ryegrass comprised 19-46% of the feed on offer in Expt 1 and 65-82% in Expt 2. Perennial ryegrass comprised 79-89% of control pastures and white clover generally comprised < 10% of all pastures. Organic matter digestibility of both the feed on offer and diet selected, determined with deer fistulated in the rumen or oesophagus, was 75-80%.In Expt 1, rates of body growth during winter were greater for stags grazing at 10 cm than at 5 cm pasture height, with no effect due to the inclusion of annual ryegrass. During spring, growth rates were similar for stags grazing 10 cm pastures and the 5 cm pasture containing annual ryegrass, but were lower on 5 cm pasture based on perennial ryegrass. Inclusion of annual ryegrass slightly increased winter rates of herbage dry matter accumulation, animal carrying capacity and the proportion of stags attaining target slaughter weight.In Expt 2, annual ryegrass pastures were of higher organic matter digestibility than perennial pastures during winter, and supported greater rates of liveweight gain (LWG) and voluntary feed intake (VFI) than the perennial ryegrass. During spring, LWG increased in both groups of stags although the difference between the two groups ceased to be significant. More of the animals grazing annual ryegrass pastures attained target slaughter weight than those grazing perennial pasture. Rumen acetate: propionate ratio, measured in fistulated stags, was similar for both groups of animals. Relative to perennial ryegrass, pastures containing high proportions of annual ryegrass resulted in similar animal carrying capacity during winter but substantially lower carrying capacity in spring.Antibodies binding melatonin were detected in 75% of immunized animals, with higher and more persistent titres being obtained using Freund's than using Dextran adjuvant and titre being much higher in stags immunized at birth than at 3 months of age. This was associated with a small and variable increase in plasma prolactin concentration, but had no effect upon plasma concentrations of LH or testosterone or upon LWG.It was concluded that the small increase in deer production attributable to annual ryegrass was mainly due to higher VFI, and that grazing perennial ryegrass/white clover pastures at 10 cm surface height resulted in higher levels of deer production than grazing at 5 cm surface height. These studies emphasise the feasibility of early v...

The effects of grazing chicory (Cichorium intybus) and birdsfoot trefoil (Lotus corniculatus) on venison and velvet production by young red and hybrid deer

“…The present study confirmed that when relying entirely on perennial ryegrass/white clover pasture for 12 month venison production, a low proportion of deer reached target slaughter LW (92 kg or greater) and carcass weights barely attained 50 kg, supporting earlier observations (Ataja et al 1992;Semiadi et al 1993). It also showed that spiker velvet antler production was low (0.2 kg/stag).…”

Effects of grazing red clover(Trifolium pratense)or perennial ryegrass (Lolium perenne)/white lover(Trifolium repens)pastures upon growth and venison production from weaner red deer(Cervus elaphus)

“…The weaner red deer showed intermediate growth during autumn, slow growth during winter, and high growth during spring in the present experiment, in agreement with the growth of farmed red deer being seasonal (Blaxter et al 1974;Drew 1976;Fennessy et al 1981;Ataja et al 1992;Semiadi et al 1993). Slow growth of the animals during winter is typical for young red deer, because of the seasonal loss of appetite (Kay 1985;Barry et al 1991), and acts as a major constraint to increasing venison production from young deer.…”

“…This resulted in high growth rates and the proportion of animals attaining target slaughter weight was an improvement on the findings of Ataja et al (1992) (41%) and Semiadi et al (1993) (75%) for young red deer stags grazing perennial ryegrass/white clover pastures (Table 7).…”

“…Earlier studies (Ataja et al 1992) showed that by feeding high allowances of pastures based upon perennial or annual ryegrass during winter and spring, respectively 41 and 60% of young red deer stags could attain this slaughter target. The present studies were designed to further extend this concept, by feeding high allowances of perennial ryegrass/white clover pasture in autumn as well as in winter and spring, and replacing annual ryegrass with red clover as a special-purpose forage for deer production.…”

“…Under current pasture conditions and management, young red deer (Cervus elaphus) stags normally reach the target slaughter liveweight (92 kg; 50 kg carcass) at 15 months of age (March) (Drew 1989), when venison schedule prices have declined. It is most profitable to produce venison from red deer in NZ with carcasses weighing more than 50 kg by just under 1 year of age, to meet the demand of Northern Hemisphere markets resulting in highest schedule prices in the August to December period (Ataja et al 1992). By offering high allowances (6.3 kg DM/ha per day) to weaner red deer stags grazing annual ryegrass pasture during both winter and spring, Ataja et al (1992) showed that 60% of animals could attain this target.…”