Estilos de aprendizaje en personas mayores

Comprehensive studies of the biology and physiology of captive tropical deer is in its infancy, with most work being conducted in non-tropical environments (Kelton 198 1 ; van Mourik 1985; Cbapple 1989; Mylrea 1992). At equatorial latitudes, ungulates are believed to have day-length­ dependent rhythms which are controlled by environmental factors such as rainfall and nutrition (Skinner 1978). Loudon & BrinkJow ( 1 992) argue that some deer species living at lower tropical latitudes also show an inherent rhythrnicity, which could be associated with the seasonality of feed intake and reproduction cycles. A transition latitude between seasonal and aseasonal reproductive cycle deer lies between latitudes 14° N and 1 8° S (Goss 1 983). Rusa stags in Victoria, Australia, are reported to have acclimatized to the local environment (van Mourik et al. 1985), as have tropical Burmese brow-antlered binds eldi in North America (Monfort et al. 1990). Sadleir ( 1987) argues that environmental factors are more important than photoperiod in regulating the tropical deer reproductive cycle. A comparative study between rusa and red stags under Australian sub-tropical environments indicates that rusa show no seasonal trend in their growth until at least 1 5 months of age (Suttie et al. 1 992a). Similar results were also found with cbital (Cbapple 1989).

To adapt to a changing temperate climate, temperate deer have a pronounced yearly physiological seasonality. Seasonal cycles present are voluntary feed intake (VFI) and body growth, velvet antler stripping and casting, replacement of coat and colour changes, fasting metabolic rate, and reproduction (Kay & Ryder 1978; Lincoln 1985; Barry et al. 199 1 ; Domingue et al. 1991a&b). With red deer, elevated feed intake and growth rate occur in spring and summer, decreasing to low values in winter (Suttie et al. 1989; Domingue et al. 1991a), with antler casting occurring in spring (Fennessy & Suttie 1985). The reproductive activity in both sexes is high during autumn/early winter (Kelly et al. 1985, Fennessy & Suttie 1985). All these seasonal cycles are regulated by hormonal changes, whilst daylength entrains the cycles (Barrell et al. 1985; Lincoln 1 985; Suttie & Simpson 1 985). Thus, the

3. NUTRITION & PRODUCTION 3.1 Voluntary feed intake pattern

6

There are no published data on the VFI pattern of tropical deer. The closest comparative study conducted was between red deer and non-tropical Asiatic Pere David ' s (PD.

A similar pattern of feed intake in both species occurred during the first autumn. Later, PD showed an earlier peak in VFI than red deer, related closely to significant changes in hormonal levels (Loudon et al. 1989). In their native habitat, Ngampongsai ( 1978) assumed no clear seasonality of VFI could be expected in sambar due to the good availability of feed throughout the year. The VFI of one captive adult sambar hind, fed roughage was 1 084 gDM/day (Ngampongsai 1978).

The pattern of VFI in temperate deer is pronounced in two years of age stags (Fennessy & Milligan, 1987), but less marked in younger deer (Suttie et al. 1 989). Peak VFI occurred during period of long daylength with low VFI being associated with decreasing daylength (S uttie et al. 1984). Both pelleted diets or natural grazing gave similar trends of feed intake, indicating that the seasonality in temperate deer is regulated by physiological aspects (Barry et al . 1 991). Red stags aged 3-15 months had an increasing feed intake soon after weaning in summer, 1 1 kgDM/week, dropping during winter to 9 kgDM/week, and rising again in spring to 15 kgDM/week (S uttie et al . 1989). This is shown in Figure 1 A Milne ( 1 980) states that the seasonal change in VFI and energy metabolism in red deer is prominent, with the changes in VFI relating to the change in the amount of digesta in rumen and rumen capacity. This was later conflflTied by Domingue et al. ( 1 99 1a), where the rumen pool size of red stags was 50% greater and the VFI was 34% higher in summer than during winter.

3.2 Growth pattern & growth rate

A study with Javan rusa hinds in Queensland, Australia, showed the highest growth rate occurred between 2- 14 months of age, usually during winter, and thereafter consistent! y declined until 26 months of age. The lowest daily growth rate occurred between 300-360 days. The reverse trend was found with rusa stags, aged between 14-26 months, with the highest growth rate occurring in autumn (212 g/day), lowest in winter (45 g/day) (Woodford & Dunning 1 992). During the rut, rusa stags could lose 1 5 % of their liveweight (Woodford & Dunning 1992), whereas chital stags lost only 5-7% (English 1 992). In chital stags, liveweight continued to increase up to five years of age, with no significant seasonal liveweight changes. Variation in liveweight between chital stags of the same age is believed to be due to the time of birth (Chapple 1 989). No information is available on the growth pattern of sambar.

Following the VFI pattern, growth in young red deer is high during spring and summer, low in winter and moderate in their first autumn (Figure 1 B , Suttie et al. 1989). Typical of adult red stags, growth ceases between 14-20 months of age, and during the rut, adult stags may lost up to 30% of their body weight (Adam 1 988). Photoperiodic effects are believed to be the major cause in slowing

Dry maner intake (kglwk) Live weight (kg) 16 _A

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15 14 SED 13

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8 7 6 0 1 00 B 80 80 70 60 SED

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50 40 30 20 10 0 N 0 J F M A M J J A S 0 N 0 J F 0 2 3 4 5 6 7 8 8 10 1 , 12 1 3 1 4 1 5 MontiVAge

Figure l .(A) Voluntary feed intake and (B) growth patterns of young red stags fed indoors on a pelleted diet ad libitum. under southern hemisphere conditions (Suttie et al.

1989).

8 growth during winter and increasing growth in spring (Suttie & Kay 1985). A comparative study of growth between rusa and red deer under a sub-tropical environment indicates that photoperiodic effects did not influence the growth of both rusa stags and binds (Suttie et al. 1 992a, Figure 2). This needs further study.

At birth, healthy red deer calves can reach nine kg in liveweigbt (Coucbman 1978), and at both birth and weaning, stag calves are usually 13% heavier than bind calves (Moore et al. 1 988a). Asber & Adam (1985) confirmed that high liveweigbt gain in red deer calves from birth to weaning is closely related to dam weight and birth weight. A Scottish study of lactating red hinds and deer calves grazing either bill pasture or improved pasture indicated no difference in liveweigbt gain between the two pasture types until 30 days of age (Loudon et al . 1984), indicating that early growth is most influenced by maternal milk production. The highest reported growth rate of farmed red deer calves is 461 g/day, when both darn and calf were grazing on red clover pasture (Niezen et al. 1993). Weaned calves grazing red clover during autumn and spring have consistently higher growth rates than those animals grazing conventional perennial ryegrass based pasture (Serniadi et al. 1993).

3.3 Carcass weight

The range of liveweight in wild sambar stags is between 1 36-350 kg, with binds between 1 1 3-225 kg (Bentley 1 978; Misbra 1 982; Douglas 1983; English 1988). Under Victorian (Australia) farm conditions, the heaviest sarnbar hind ever recorded was 228 kg (Anderson 1984). On the other hand, the range of liveweight in wild red stags is between 1 35-227 kg, and in hinds between 1 14-1 52 kg (Couchman 1978; Kay et al. 1984). Mature liveweight of farmed red stags and hinds aged three years can reach up to 1 80 kg and 1 10 kg, respectively (Couchman 1978).

Premium are usually paid for carcasses in excess of 50 kg (92 kg liveweight), which, . generally can be achieved at 15 months of age. Through better pasture improvement, the time to achieve optimum carcass weight can be shortened to 12 months of age for red stags. Carcass dressing percentages in red deer are 53-55% (Ataja et al. 1 992; Semiadi et al. 1 993). With Javan rusa, the carcass dressing percentages were recorded as 62% (Woodford & Dunning 1 992), and 60% for cbital (Chapple 1989). Carcass weights for mixed age wild sambar killed by local people in east Kalimantan (Indonesia) have been up to 1 1 5 kg in stags and 1 05 kg in hinds (Sukmaraga 1 982).

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