Nutrition of Farmed Deer

Robert J. Hudson
Department of Renewable Resources
University of Alberta
Edmonton T6G 2H1
[Proceedings of the Western Nutrition Conference]

Introduction

There are now almost 100,000 farmed deer in Canada and the population continues to compound at about 20% per annum (Hudson and Burton 1993). This is part of a worldwide wave that has seen numbers increase exponentially from several thousand in 1969 to about 3 million today (Hudson 1993). There is good reason for this interest. Deer farming offers Canadian farmers an opportunity to tap new markets (venison, velvet) and to develop relatively low-input seasonal pasture-based management systems (Friedel and Hudson 1994).

The main deer (cervids) farmed in Canada are wapiti (Cervus elaphus canadensis), red deer (C. elaphus), fallow deer (Dama dama), white-tailed deer (Odocoileus virginianus) and reindeer (Rangifer tarandus). Curiously, inconsistent government regulations mean that different species are farmed in each province. For example, only fallow deer and reindeer are raised in British Columbia, only wapiti, white-tailed deer, mule deer (O. hemionus) and moose (Alces alces) in Alberta, fallow and native deer in Saskatchewan and essentially none (except under special permit) in Manitoba. Most red deer are farmed in eastern Canada where there is no danger of interbreeding with wild wapiti.

Worldwide, deer are raised under a variety of circumstances. They are hand-fed throughout eastern Asia, grazed on improved pastures in Europe and New Zealand, and ranched on native ranges in Russia. In Canada, deer farming has tended to follow the New Zealand model but is constrained by seasonal pastures and the need for winter feeding.

Increasingly feed companies are being called to provide nutritional advice and to provide feeds for these unfamiliar ruminants. The objective of this review is to: (1) establish differences between deer and conventional farm livestock, and (2) lay some groundwork for developing international feeding standards. Most work on deer nutrition is based on the British Metabolizable Energy System and most published information is in SI units (kJ or watts). This article draws heavily on Haigh and Hudson (1993).

Nutritional Ecology

Although deer farming dates to ancient times, little has fallen within the "scientific" era of animal nutrition (Hudson et al. 1989). To what degree can nutritionists instinctively apply research and experience gained with conventional farm ruminants? Probably quite well if several underlying gradients of adaptation are understood.

Feeding behavior and digestive adaptation

Wild ruminants are adapted to almost all of the world's biomes. The basis of their remarkable dietary specialization has been elucidated by the classic morhophysiological research of Hofmann (1989). On the basis of digestive anatomy, he classifies the world's ruminants as concentrate selectors (browsers), roughage feeders (grazers) and intermediate feeders. The extremes are typified by the white-tailed deer (browser) and bison (grazer).

The white tailed deer relies heavily on browse (foliage in summer and twigs in winter) and high quality fruits, nuts, seeds, and forbs. The muzzle is long and narrow and the incisor bar is curved facilitating selective feeding. The molars are relatively low crowned. Salivary glands are large and produce serous saliva with proteins that complex tannins. The gut is small relative to body weight and the rumino-reticulum is small relative to the total digestive tract. The reticulo-omasal orifice is large allowing passage of large forage particles. The cecum is well developed. Similar digestive anatomy is seen in mule deer and moose.

Bison, on the other hand, are adapted to grasses and sedges which are consumed in all seasons. The broad muzzle and flat incisor bar limit selective grazing but allow efficient feed intake on short grazing "lawns". The salivary glands are relatively smaller rumen and saliva does not complex tannins as well as in browsers. The molars are high-crowned to accommodate the greater wear associated with the silicacious graminoids and the grit consumed while grazing. Because rumen contents are stratified, ruminal papillae vary in length and density from the bottom to the top of the rumen. The rumino-reticulum is enormous (contents comprise up to 25% liveweight). The communication between the rumino-reticulum and omasum is constricted delaying passage of larger particles. Other examples of grazers (but somewhat more selective ones) are domestic cattle and sheep.

Most deer raised on Canadian farms are mixed feeders. Their digestive anatomy is intermediate and changes strikingly in response to seasonal diets. Wapiti, quintessential mixed feeders, require slightly more fiber than red deer and a great deal more than white-tailed deer. Despite their smaller body sizes, fallow and sika deer approach sheep in their digestive characteristics and hence requirements for fiber.

Functional characteristics reflect this anatomical design (Renecker and Hudson 1990). Browsers are best adapted to forages with rapid initial fermentation but low asymptotic digestibility. They skim readily digestible nutrients and propel refractory particles rapidly through the digestive tract so distension does not limit intake. Grazers, on the other hand, do best on forages such as grasses that ferment slowly but more completely. Mixed feeders probably use each feed type less well but benefit from greater nutritional flexibility.

Seasonal metabolic adaptation

The most remarkable adaptation of cervids is well-developed seasonality of metabolism and productive functions. Cycles appear strongest, as expected, among deer at higher latitudes. Tropical deer such as the axis (Axis axis), sambar (Cervus unicolor) and rusa (Cervus timorensis) are considered non-seasonal. Fallow deer are Mediterranean in origin and are less seasonal than boreal and arctic deer.

Because these cycles are characteristic of northern wild ruminants, logic suggests that bioenergetic cycles are adaptations to meager winter feed supplies. However, evidence now points to the primary selective advantage of rapid maturation during the brief flush of summer vegetation. Another debate has been whether appetite, metabolic demand or productive functions drive the circannual bioenergetic cycle. Although cause and effect have not been resolved, progress has been made in understanding endocrinological controls. The central mediator of photoperiod sensitivity is melatonin. Other important metabolic hormones include prolactin, thyroid hormones, IGF1 and, in males, testosterone.

Appetite- Appetite is strongly seasonal with the peak at the summer solstice and minimum near the winter solstice in females and during the rut among mature males. It correlates directly with blood levels of prolactin and inversely with melatonin (or testosterone in the case of males). Appetite differs at least 1.4-fold between winter and summer in non-breeding animals. Lactation increases dry matter intakes by about 2-fold.

Metabolic rates- Energy expenditures also show seasonal cycles although the cycle is strongly influenced by feed intake, thermoregulation, and activity. The most direct way to determine seasonal maintenance requirements is to estimate feed required to maintain body weight. Values derived this way for wapiti (Table 1) confirm the existence of an independent seasonal cycle and give an impression of the energy costs of free existence which include incremental costs of both thermoregulation and activity (Jiang and Hudson 1994). Surprisingly, the incremental costs of free existence appear greater in summer than in winter. The reason seems to be that in winter animals that are supplementally fed are inactive during cold and snowy weather choosing to bed around feeding stations.

Table 1. Metabolizable energy requirements of wapiti for maintenance and gain (Jiang and Hudson 1994)

Maintenance (kcal/kg0.75/d) Gain (kcal/g)

Winter Penned 113 7.9 
 Pastured 119 6.0 
  
Summer Penned 174 9.8 
 Pastured 235 9.6 
 

costs of thermoregulation presumably vary with feeding level as well as body mass (hence species) and quality of the hair coat. White-tailed deer and fallow deer are most sensitive to cold. But cold stress can be high enough to warrant in-wintering red deer calves in Scotland and, at least sheltering in most other areas. Even in still air, the lower critical temperature of red deer stag calves is +5[[ring]]C, which makes them much more cold sensitive than young sheep and cattle. Adults, of course, are more resistant to cold.

Wapiti are larger and better insulated (Parker and Robbins 1985). Although wapiti calves have lower critical temperatures of -20[[ring]]C when bedded, it rises to -5[[ring]]C when they are standing or active (Fig. 1). Protected from wind, adults are very resistant to temperatures as low as -25[[ring]]C. Despite cold (but dry) climates, wapiti seem only to require shelter from wind and long-wave radiation.

Growth - Growth of deer is seasonal (Fig. 2). Winter weight stasis is followed by compensatory summer growth. There seem to be seasonal set points of body weight which lead to a rather remarkable symmetry in the relationship between minimum spring weights and subsequent peak fall weights (Fig. 3).

Fig. 1. Energy expenditures in relation to ambient temperature for wapiti calves while active , standing or bedded (Gates and Hudson 1979).

Fig. 2. Seasonal cycles of body weight in a wapiti stag from birth to maturity. Weight gradually increases until about 8 years of age.

Fig. 3. Liveweight gains of lactating (milk) and dry (yeld) wapiti females on summer pasture.

Fig. 4. Compensatory gain of yearling wapiti stags on summer pastures (Wairimu et al. 1992).

This relationship is of considerable practical significance. Compensatory gain provides an opportunity for savings on winter feeding and for capitalizing on summer pastures (Fig. 4). However, particularly in young stock, the capacity to recover weight is not infinite.

ME requirements for liveweight gain of wapiti range from 6 kcal/g in winter to almost 10 kcal/g in summer (Table 1). Research on red deer at Invermay, New Zealand (Fennessy et al. 1981, Suttie et al. 1987) determined a value of 8.8 kcal/g for 6-18 month-old stags and 13 kcal/g for hinds.

Reproduction - Perhaps the most important aspect of seasonal adaptation is reproduction. Calving must be precisely timed to ensure that calves miss late winter storms but still have time to mature sufficiently to survive the following winter. The rut, obviously, peaks a gestation-length before the optimal calving sate. Since this optimum is late May/early June in western Canada, the rut falls in the 3rd week of September for wapiti (255 days gestation), October in red deer and fallow deer (230 days) and November in white-tailed deer (205 days). The relatively long gestation of wapiti gives them more time to regain post-rut condition before winter

Demands of gestation are light until the third trimester when pregnant females already have access to spring pasture. In the final days of gestation, energy requirements increase to 1.2 Mcal/day for red deer and 2.9 Mcal/day for wapiti. Not all of this must come from feed. To minimize calving difficulties, larger hinds should meet some of these needs by mobilizing body tissues.

During the first month of lactation, red deer milk contains 8-13% fat, 7-9% protein, and 4.5% lactose. Wapiti milk is slightly more dilute at a comparable stage of lactation (Kozak et al. 1995). As milk production declines through lactation, the energy concentration of red deer milk increases from 1 to 1.7 kcal/g. Wapiti milk seems marginally less concentrated especially in well-fed high-yielding animals (>4 kg/d) but averages about 1.2 kcal/g (Hudson and Adamczewski 1990, Kozak et al. 1995).

Despite the higher energy value of deer milk, the daily energy yield at peak lactation (volume x energy value) conforms closely to interspecies allometry. On good nutritional planes, red deer produce about 2.5 liters and wapiti about 4 liters of milk daily at peak lactation. This level of milk production supports an average daily rate of gain of about 280 g/d in Scottish red deer, 320 g/d in New Zealand red deer, and 870 g/d in wapiti calves until pre-rut weaning at about 110 days of age (early September).

Nutritional plane has modest effects on milk production and even less on the growth of calves (Hudson and Adamczewski 1990).The most powerful effect on calf performance is birth weight. In wapiti, every kg increase in birth weight compounds to 3.7 kg by weaning at 110 days.

For stags, antlers are an investment in reproduction because they play a role in establishing dominance and gaining access to estrous females during the rut. Red deer antlers may grow an average of 100 g/day. Daily ME requirements for antler growth (2.9 kcal/W^0.75) are a small fraction of the daily energy budget: 120 kcal/d for red deer to perhaps 240 kcal/d for wapiti.

The response of velvet growth to improved nutrition is modest in well-grown animals. Pre-rut weight, probably more specifically frame size, is the main determinant and each 10 kg increase in pre-rut body size advances the date of casting 3-4 days and velvet weights by 0.12 kg.

Feeds and Feeding

Projecting feed requirements involves three steps: (1) calculating nutrient requirements, (2) estimating the pasture supply, and (3) calculating the shortfall to be made up with supplemental feed.

Seasonal nutrient requirements

Seasonal target weights and metabolizable energy requirements for red deer and wapiti are summarized in Table 2 (Haigh and Hudson 1993). Information for white-tailed and fallow deer remains incomplete. As in red deer, there is considerable variation in mature size among fallow genotypes and they are among the most sexually dimorphic deer in terms of size.

Target weights - Deer should be fed to attain seasonal target weights (Table 2). Such targets are specific to each genotype and therefore these numbers are indicative of the most commonly farmed races, the Rocky Mountain wapiti and New Zealand red deer.

Fig. 5. Probability of conception of wapiti in relation to rut weight. Wapiti must reach approximately 210 kg to achieve 50% conception rates (Hudson et al. 1991). Conception rates approach 95% in animals exceeding 260 kg. Weaning rates of adult hinds in Alberta average over 90% (Friedel and Hudson 1994).

Seasonal target weights of calves are selected primarily to ensure puberty and maximize conception rates at 15 months of age (Fig. 5). Target weights for hinds are selected to minimize calving difficulties due to overfeeding during gestation and to ensure recovery of body condition during lactation to conceive in the ensuing rut. Targets for stags are selected mainly to ensure post-rut recovery, velvet growth and regaining of rutting condition. Since wapiti stags mature late in life sometimes achieving weights up to 500 kg, it is difficult to summarize seasonal weight targets for "adult" stags.

Energy allowances - Seasonal energy requirements of red deer and wapiti differ mainly in scale rather than seasonal pattern. Because of allometric scaling, daily requirements of wapiti hinds are only twice that of red deer despite 3-fold greater weight. The weight difference of stags is about 2.5-fold but requirements differ by only about 1.8-fold.

Because of their shorter gestation, red deer rut several weeks later. This means that red deer stags have less opportunity to recover condition, generally go into winter in poorer condition and, consequently, require better nutritional support. Wapiti stags usually recover some rut weight loss before the winter solstice.

White-tailed and fallow deer may have higher winter requirements under farm conditions but largely because of greater activity, nervousness and thermoregulatory increment. Summer requirements may be higher because of relatively greater demands of reproduction in small animals and exceptional rates of liveweight gain.

Protein allowances - Protein requirements are less well defined than energy requirements and there is still no reason to expect species differences except for reindeer and caribou which are adapted to lichen diets (Mould and Robbins 1981). The objective of protein supplementation is to precisely meet the animal's needs for amino acids since above this level, feed protein (generally, an expensive feed ingredient) is used as an energy source. Also, excessive protein consumption by stags can result in prepucial ulceration and prolapse from ammonia burns on the penis sheath.

For their first year of life, deer benefit from protein levels of up to 16% protein. Other classes of stock should receive these levels only in spring and early summer when their demands are high. Winter maintenance requirements of adults are fully covered with protein levels of 8-10% although attention to palatability is necessary.

Mineral nutrition - There is little research that suggests requirements of red deer and wapiti for minerals are different than domestic stock. One exception seems to be their high requirement for copper (also perhaps selenium) and relative tolerance of copper toxicities. Recommended dietary levels are over 15 ppm for copper depending on mineral interactions. This generalization may not be safe for fallow deer (Reinken 1990).

Table. 2 Seasonal target weights (kg, normal type) and metabolizable energy requirements (Mcal/day, bold type). Modified from Haigh and Hudson 1993).

Hinds Stags

Feeding Periodsa 3-15 mo 15-27 mo Adult 3-15 mo 15-27 mo Adult 
WAPITI  
Autumn (1 Sep-1 Nov) 110b 220 290 120 280 365 
 6.5 8.4 9.3 7.6 7.9 9.6 
Winter (1 Nov-1 Apr) 130 225 290 150 260  340 
 6.7 7.6 8.4 7.6 9.3 11.5 
Spring (1 Apr-15 May) 150 225 270 168 260 340 
 9.8 12.0 12.2 12.9 14.1  12.7 
Summer (15 May-1 Sep) 168 230 275 195 266 346 
 11.7 19.1 20.0 16.3 13.9 11.7 
  
RED DEER 
Autumn (1 Sep-1 Nov) 43 85 95 48 105 190 
 3.6 5.5 5.5 3.8 5.7  4.5 
Winter (1 Nov-1 Apr) 50 85 90 60 93 150 
 4.3 5.3 5.3 4.5 6.7 8.4 
Spring (1 Apr-15 May) 60 86 86 70 93 150 
 5.3 5.7 5.7 6.5 7.4 10.0 
Summer (15 May-1 Sep) 68 88 88 80 98 152 
 5.0 11.2 11.2 6.2 7.2 9.1 
 
 

Feeding periods (seasons) are defined for wapiti in western Canada as follows: Autumn (1 Sep-1 Nov) runs from the onset of the rut to the start of winter feeding. Winter (1 Nov-1 Apr) is the period of snow cover. Spring (1 Apr-15 May) is signaled by snow-melt and the flush of green vegetation. Summer (15 May-1 Sep) extends from calving to the rut.

^bWeights at beginning of each period

Nutrient supply from range and pasture

If ranges are not overstocked, most of a deer's seasonal nutrient requirements can be met by grazing. Of course, the adequacy of the nutrient supply from forage depends on both its quality and availability.

Dry matter intake - Within limits, deer can compensate for deteriorating diet quality simply by consuming more. But, low quality forages ferment and pass from the rumen slowly and intake becomes limited by gut fill. Although not quantified, rumen capacity seems to increase under these circumstances and also during lactation to accommodate higher intakes. Stemmy pastures impose quality limitations and should be mowed or grazed by cattle or bison (leafy pastures should be grazed first by deer than by large grazers).

Nutrient intakes on pasture are influenced by logistic as well as digestive factors. Pasture biomass/structure and snow cover are most important. The feeding rate on foliage and browse is not very sensitive to biomass because of the clumped distribution of these forages. However, intake on grass pastures is determined largely by standing crop (Fig. 6). The feeding rate of wapiti is reduced to 50% at about 850 kg/ha (Hudson and Watkins 1986). Wapiti compensate by grazing longer but reach an upper limit of about 12 hours/day. The general recommendation for deer during periods of rapid growth is to manage pastures to provide at least 1200 kg/ha or a sward depth of about 10-15 cm (4-6 inches).

Fig. 6. Feeding rate of wapiti on cured (top line) and green (bottom line) bluegrass/bromegrass pastures (Hudson and Watkins 1986).

Native ranges - On parkland ranges in western Canada, wapiti use most habitats at some time of the year. Sedge meadows provide the earliest spring forage. Wapiti then shift to upland grasslands beginning on the slopes and following snowmelt into lower areas. As pastures mature in July and August, wapiti shift to foliage in aspen forests, returning to grasslands during the rut. Leaf litter makes an important contribution during early winter but snow conditions later in the year shift dependence to browse in willow and aspen communities.

Despite their somewhat lower productivity, native pastures supply a variety of forages which extend the grazing season (Fig 7). Certain forage classes such as leaf litter (1200 kg/ha in typical aspen forests) can make an important contribution to early winter carrying capacity for wapiti but little for cattle. This makes it difficult to assign an animal unit equivalent which would apply across all pastures.

Fig. 7. Quality of seasonal forages used by wapiti in aspen habitats in western Canada (Renecker and Hudson 1988).

Tame pastures - New Zealand pasture production is based largely on perennial rye grass although it is not particularly preferred by red deer whose appetite and performance improve on more diverse swards containing red or white clover or chicory. Many pasture species better adapted to our climate and soils are suitable for deer. The choice should be based on agronomic considerations as much as preferences of the deer. There is such wide geographic variation that prescriptions are best left to local agricultural extension officers.

Making up the difference

Supplementary feeding serves three functions: (1) to habituate and control animals, (2) to correct seasonal deficiencies in pasture, and (3) to increase carrying capacity. For the first reason, small quantities of grain or pellets should be offered throughout the year.

Supplemental feeding - The amount and nature of supplement is determined by the shortfall of pasture forage. Although the requirements of animals for energy and protein are known rather precisely, the proportion obtained from pasture can only be very crudely estimated because animals can offset poor foraging conditions by feeding in better habitats or grazing longer. Also, heavy supplementation with palatable feeds reduces dependence on pasture forage (Kozak et al. 1994).

Supplemental feeds - Shortfalls in pasture can be made up with a variety of conventional feedstuffs although attention to quality and palatability is more important than it is for beef cattle. Tables of ME values of feeds intended for sheep seem work well enough with deer.

Local available grains are good energy sources for supplements. Oats are preferred because of their bulk and energy concentration. There are fewer problems with over-consumption and adjustment to oat-based rations. Although utilization may be better with ground or rolled oats, whole oats are routinely fed by wapiti farmers. Barley and maize also have been used with care to prevent initial overfeeding.

High protein diets are often fed to encourage velvet growth. In the Orient, protein sources include leaves and leaf meal, and full-fat soybeans soaked in water. In North America, dehydrated alfalfa and oilseed meals such as soybean or canola are used as protein sources but palatability can be a problem, especially with high levels of canola. Current research by Renecker and graduate students on fish meals for venison and velvet production suggests that deer are sensitive to protein quality.

One of the most promising supplemental feeds for deer and other concentrate selectors and mixed feeders is processed alfalfa. The rapid but low asymptotic digestion simulates the diets to which they are naturally adapted. Initially, industry attention was directed to strong Asian markets but local game farmers have shown considerable interest and created significant demand.

There is little difference in utilization of dehydrated alfalfa pellets, standard cubes, and small cubes. The mean retention time of processed alfalfa is 25 h, apparent dry matter digestibility is 50% and protein digestibility is 65%. The main determinant of digestibility is neutral detergent fiber rather than physical form (Fig. 8). Because all processed alfalfa products are dense, feeding rates are high. Alfalfa also is used extensively in compounded diets. The diet in Table 1 serves as an adequate complete feed for white-tailed and mule deer or supplement with forage diets for wapiti, red and fallow deer.

Fig. 8. Dry matter digestibilities in relation to neutral detergent fiber content of various forms of alfalfa (pellets, cubes, baled hay and compounded feed).

Although convenient, pelleted feeds can be expensive, used inefficiently, and may lead to overfatness of hinds. Consequently, many wapiti farmers offer grass/legume hay, mineralized salt, and whole oats (offered in small quantities to habituate animals) as wintering rations for adult stock. Despite higher intakes and greater use of pasture, pellet-supplemented hinds divert most of this additional energy to activity (Kozak et al. 1994). Dystocias and lactation failure seem to follow harsh winters where animals stand around feeders overfattening on concentrate rations (Kozak et al 1995).

Prospects

The deer industry is here to stay. It is difficult to know where it will stabilize but it will, by tapping niche markets, provide badly needed agricultural diversification for prairie farmers. Feed company representatives should be prepared for increased involvement.

Table. 3. Ingredients and analysis of compounded cervid diet used at the Ministik Field Station

ITEM (kg/tonne)

Dehydrated alfalfa 255 
Barley  310 
Wheat shorts (middlings) 140 
Soybean meal (48% CP) 85 
Beet pulp 160 
Molasses 40 
Trace mineralized salt  4 
Vitamins A,D,E mix 2 
Binder/anti-mould 1 
 
ANALYSIS (%) 
Protein  16.6 
Neutral detergent fiber 27.2 
Acid detergent fiber 16.8 
ME (kcal/g) 2.8 
 
 

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