CHAPTER 128 Reproductive Management of Farmed Red Deer and Wapiti
Currently, the various races or subspecies of red deer, and the wapiti (or North American elk), which is found in eastern Asia as well as North America, are all considered to belong to one species, Cervus elaphus.
The historical range of red deer stretches from Scotland to China, with perhaps as many as 22 subspecies recognized.1 Red deer have been introduced into the wild in numerous countries. They have been domesticated as a livestock species in many countries, but particularly in New Zealand, where approximately 2.3 million animals were farmed in the year 2001.
Wapiti, of which at least 10 subspecies are recognized, range, in Asia, from the Tien Shan mountains of Russian Turkestan and the Altai mountains of Russia and Mongolia through China and Manchuria into North Korea.1 In North America they were formerly found throughout much of the continent. Their range was reduced through overhunting in the late 19th century, but numerous reintroductions have occurred since. They are now found, both free-ranging and on ranches and farms, in many areas.1
Reproductive management of C. elaphus varies somewhat according to the region or country in which these animals are farmed and is influenced both by market forces and by climate. The numerous subspecies can interbreed freely. For this discussion, crosses between them are referred to as crossbreds, rather than the more commonly used, but technically incorrect term, hybrids.1 One anomaly discussed in more detail in these pages is that red deer and wapiti respond differently to ovarian superstimulation.1
Fundamentally, the species is described as seasonally polyestrous, or a short-day breeder, with the onset of fertility and the rut occurring in autumn. The timing of onset of the breeding season has evolved by the need to deliver calves at a time when grazing conditions are optimum for milk production and calf well–being, in early summer. Gestation of wapiti is slightly longer (247 ± approx. 5 days) than that of red deer (233 ± approx. 7 days).1,2 For this reason wapiti stags clean the velvet antler (an event closely linked to elevated testicular testosterone concentrations) and display aggressive behavior prior to the rut, about 2 weeks earlier than red deer.1
BODY CONDITION AND BODY CONDITION SCORING
Body condition score (BCS) is an important tool for management of dairy and beef cattle. BCS systems have been developed for both red deer and wapiti.3–5 Scoring charts have been developed with scores ranging from 1 (lean, or very poor condition) to 5 (fat, or very good condition) with half-unit increments3,5 or from 1 (thin or emaciated) to 9 (fat or obese).4 For the purposes of the following discussion the 5-point scale of Audigé and associates3 is used. It is essential that palpation be employed for accurate estimation of condition, particularly in winter when coat obscures the body contour. As the winter coat is usually well developed by the onset of the rut, the time when a BCS is most relevant, care must be taken to avoid missing subtle changes.6,7 Eye appraisal of animals in the paddock may estimate herd status to within one score, but is inadequate for individual animal condition scoring.
In the most objective study reported, in which deer were palpated,3 showed repeatability was 0.91 and 0.89, while reproducibility was 0.81 and 0.79 for yearlings (primiparous) and adult hinds, respectively. There were significant variations among hinds according to season and farm.
Stags
Males should enter the rut with a BCS as close as possible to 5 because they will lose from 25% to 30% of their pre-rut weight, even if offered grain and good quality hay, often resulting in a BCS of 1.5 or 2 in the early winter. In mature stags this change is seen even if the stags do not have access to hinds, as they spend considerable amounts of time engaging in rutting behavior. Yearling stags (18 months of age) do not lose appreciable weight or BCS during this period, and 2- and 3-year-old stags lose about 15% of body weight.
Stags require a high plane of nutrition immediately after the rut to recover adequate condition before winter, to reduce the risk of death due to exposure. Grain or concentrates or high pasture allowances should be provided for at least 6 weeks before the winter solstice. By this time, animal and human safety is usually not a problem, as aggressive behavior has subsided. A useful target by the winter solstice is a recovery of 25% to 30% of the body weight lost, or a BCS increase of 1 point. Gradual increase in grain allowance avoids grain overload and laminitis, to which deer are particularly susceptible.1
Hinds
Body Condition Score and Conception
In red deer, premating BCS is significantly associated with conception rate, conception date, and weight of weaned offspring, while BCS during pregnancy is associated with dystocia and ability of the red deer hind to rear a calf to weaning.3,8
Guidelines for achievement of optimal reproductive performance have been proposed. In general, hinds with a BCS of 2.5 or more have a greater chance of conception per se, and have an earlier conception date. Pregnancy rates of hinds in good condition (3–5) are likely to be 10% greater than hinds in poor condition (<2.5).9 However, it has been observed that overfat primiparous hinds (>BCS 4) were at increased risk of failure to conceive.6,7,10 However, Beatson and associates11 were unable to verify this relationship.
If the production target is “optimal” reproductive success, defined by an early mean conception date and high conception rate, individual hind BCS should be greater than 2.5 before mating and should either be stable or increased during the mating period.6,7 Indeed, Audigé and associates3 propose that for optimal reproductive performance from hinds, their body condition should remain stable throughout the year at scores between 2.5 and 4. Recent studies have shown that a delay in mean conception date of 12 days was associated with late weaning, resulting in an average loss of 0.5 BCS.12 The pattern of change during the mating period is also important. Beatson and associates9,11 showed that hinds below a BCS of 2.5 before mating, but increasing BCS during the mating season, have a higher conception rate than those staying below 2. Those at or above BCS 2.5 that gained in BCS during mating had no improvement in conception date or rate, confirming that BCS 2.5 or greater is optimal. However, these authors demonstrated that hinds losing BCS from any premating score showed a lowered conception rate. These observations confirm the value of BCS as a predictor of reproduction outcomes, and as a tool for determining when management changes are appropriate if optimal reproductive performance is desired.
Similar criteria for wapiti have not yet been verified, but the principles are likely to be the same. Although 2-year-old wapiti hinds (jinnocks) calved (in the Northern Hemisphere) later than adult hinds (mean 11 June versus 6 June), hind pre-rut weight influenced calving dates.13 This finding confirms that there is an interaction between BCS and body weight, particularly in primiparous hinds.
Body Condition Score and Dystocia
It has been generally believed that the fat, unfit hind is more likely to suffer dystocia than one that is physically fit and in optimal body condition.1 Recent research has shown associations between BCS and dystocia in red deer herds.8 Hinds with a BCS of 4 or more shortly before calving were 2.7 times as likely to experience dystocia than hinds with lower scores. An increase in BCS late in gestation also increased the risk of dystocia. There was an interaction between BCS and topography, with hinds with a high BCS but grazed on steep hill pastures being at lower risk of dystocia than hinds of the same BCS grazing flat pastures.
GENETIC SELECTION
Selection criteria for red deer have been developed, to some extent, in New Zealand. For practical purposes, the selection criteria applied by most deer farmers are quite basic. For hinds and stags, temperament is a prime determinant. This is judged by ease of handling for routine procedures such as yarding, vaccination, parasite control, ultrasound scanning, and for stags, velvet antler removal. An important consideration is aggression, both toward handlers and toward other deer. The heritability of temperament not known, and traits may be learned rather than genetic. However, farmers report a significant improvement in achieving calm, amenable deer as a result of culling animals that do not confirm to requirements. Selection of hinds for ability to conceive, as shown by ultrasound scanning early in gestation, and rear a calf to weaning, determined by lactational status, is also widely practiced. Audigé and associates6 demonstrated that hinds that reared a calf to weaning were 3.1 times as likely to conceive early, and 3.7 times as likely to conceive at all in the subsequent breeding season than hinds not rearing a calf to weaning. Some farmers using individual sire mating systems will select stags on the basis of their apparent fertility, measured by conceptions or calves born.
Selection of sire stags for velvet antler production is commonly practiced, and this has the potential for significant improvement in antler production because the heritability is about 0.43. Currently, phenotypic characteristics of weight and conformation are the main criteria. Calculation of breeding values based on individual animal recording is only recently being adopted by some deer stud farmers in New Zealand. Sire referencing now needs to be undertaken to improve the rate of genetic gain.
HERITABILITY
There have been a few studies of heritability in red deer in New Zealand and the United Kingdom. Where stag herds are farmed for velvet antler production, producers are interested in selection of stags for superior lifetime performance and selection of sires and dams to produce improved sons and management of the stag herd to increase returns from velvet antler.14 These authors found that the heritability of antler production studied among over 2000 stags on five farms ranged from 0.43 (±0.09 SE) to 0.85 (±0.33 SE). The average estimated genetic correlation between velvet weights in successive years was 0.97 (±0.07 SE) but declined to 0.76 (±0.29 SE) as the number of years between harvests increased.14
Live weights have moderate to high heritabilities in both sexes and at all ages with estimates ranging from 0.48 (±0.36) to 0.80 (±0.12)14 and 0.31 to 0.49, 0.22 to 0.89, 0.33 to 0.48, 0.37 to 0.45, and 0.37 to 0.90 for birth weight, weaning weight, midwinter weight, turn-out weight, and other weights, respectively.15 On one property where inbreeding was recognized as a factor, heritability estimates were very low (<0.08).15 Heritabilities for date of calving were low on seven of the eight farms (<0.05), and repeatabilities were low to moderate (0.06 to 0.37).15
Animals whose bloodlines originated in the forests of Eastern Europe (Yugoslavia, Hungary, Germany) were heavier at all stages, indicating their usefulness as “terminal sire” breeds, confirming the potential usefulness of the larger mainland European red deer.15 Hinds of mainland European parentage also tended to calve earlier.15
There is only limited information on heritability of production traits in wapiti. One study of heritability of antler traits in over 12,700 stags showed a moderately heritable figure of 0.27 (±0.03 SE).16 Antler yield can therefore be expected to respond to selection to some degree, but nonadditive and environmental effects can also influence production.
MATING MANAGEMENT
Although some producers do request a prebreeding sire evaluation, the semen testing of stags just before the rut is probably not a common practice, despite the fact that infertility in stags is recognized. Brucella ovis has become recognized in New Zealand as a pathogen that affects the reproductive system of stags and is capable of causing infertility.17
Stag/Hind Ratio
The mating capacity of stags is not well documented but is an important consideration in determining pregnancy dates and herd conception patterns. The average stag/hind ratios for adult and yearling red deer in New Zealand were 1 : 40 (range 8–82) and 1 : 27 (range 1–51), respectively. The most recent data has shown pregnancy rates and dates were similar for more than 80 groups of red deer hinds mated at single sire ratios as low as 1 : 140.11,18 Thus, the mating capacity of stags is greater than commonly utilized. It is recommended that all management factors for achieving pregnancy, as described elsewhere,6 be optimal when large numbers of hinds are mated to an individual stag. There are obvious advantages to the use of large mating groups. The number of paddocks needed is reduced, more hinds can be mated to superior sires, and the number of breeding stags required is reduced. However, as Beatson and associates9 suggest, the use of large breeding mobs increases the risk of financial loss if, in a single sire mating system, a stag is either infertile or subfertile. Stag failures do occur, regardless of breeding group size, so the use of back-up stags should be standard practice if the risk is to be reduced.1,9 There are no data to indicate a usable maximum number of hinds per stag on wapiti farms.
Despite the observation of a greater mating capacity of stags than commonly believed, it has become common practice to manage breeding groups with about one mature stag to 60 red deer hinds6 and about a maximum of 35 or 40 wapiti hinds. In the most extensive investigation to date, over 3600 red deer hinds over 2 years of age, and more than 1100 yearling hinds were mated in each of 3 successive years. The number of hinds per stag was classified as 0–60, 61–100, and above 100. The variations in calving dates about a median were 10.0, 10.3, and 11.3 days, respectively.9
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