Abstract

With a view to establishing the time of standing estrus in a commercial herd of wapiti (Cervus elaphus), estrus was synchronized a total of 47 times among 23 multiparous hinds over a 3-year period. All hinds were multiparous females selected for entry into an artificial insemination (AI) program. Progesterone containing (9%) intravaginal devices (CIDR) were inserted on day 0 and the hinds were placed in a paddock with a vasectomized experienced stag. On day 14 the CIDRs were removed between 2000 hours and 2100 hours, and each hind was treated with PMSG. The stag was marked with raddle paint. The hinds were checked at dawn, mid-day, and dusk for paint marking over the flanks or rump. Paint marking was taken as evidence of standing estrus. Insemination was carried out during a 60–63-hour period after CIDR removal. The overall conception rate as judged by ultrasonography was 74% but the calving rate was only 64%. Of the six twin conceptions only one came to term as twins, another as a single calf. The other four animals that had twin conceptions did not carry to term and one of these has remained barren.

Introduction

Artificial breeding of wapiti (Cervus elaphus) in North America is now a commercial success. Several hundred inseminations have been carried out in the last 5 years (Bringans personal communication). Artificial insemination is used primarily in order to try and achieve larger sets of antlers in male progeny. For convenience and because estrus detection without teaser stags is difficult, hinds are synchronized and time inseminated.¹

There are no objective indicators of genetic quality in wapiti in North America, although sire referencing schemes have been developed in New Zealand in the conspecific, but much smaller, red deer.¹ North American wapiti sires are selected solely on phenotypic characteristics. The main criteria in the marketplace are either the velvet antler weight and character, or the hard antler score. Both are judged in one of several continent-wide competitions sponsored by regional or provincial breeders’ associations and all coordinated under the umbrella of the North American Elk Breeders Association.

Materials and Methods

The criteria for selection into the program included a multiparous history, with no record of calving trouble, a quiet nature and ease of handling, and the desired genetic background. Hinds were also selected only if their body condition score was between 3 and 4 (scale 1–5; 1 being very thin, 5 being overfat). Each hind is reported as a different case for each year unless otherwise indicated.

To establish the time of standing estrus after synchronization in a commercial herd of wapiti, estrus was synchronized with a regime that involved the use of a device containing 9% progesterone into the vagina (CIDR, CHH Plastic Products, Hamilton, New Zealand) and the administration of PMSG at the time of CIDR removal. CIDRs were inserted on day 0 and the hinds were placed in a paddock with a vasectomized experienced stag. On day 14 the CIDRs were removed between 2000 hours and 2100 hours, and each hind was treated with PMSG (210 IU in year 1, 200 IU in year 2, and 190 IU in year 3).

Estrus was synchronized a total of 47 times among 23 multiparous hinds, 12 hinds in year 1, 16 hinds in year 2, and 19 hinds in year 3. All hinds were multiparous females selected for entry into an artificial insemination (AI) program.

As soon as the hinds had been treated and released back to their paddock, the stag had a mixture of automotive grease, engine oil, and blue paint smeared over its ventral thorax, medial forelegs, and anterior hind legs above the stifles. The animal was then returned to join the hinds. The hinds were checked at dawn, mid-day, and dusk for paint marking over the flanks or rump. Paint marking was taken as evidence of standing estrus.

Insemination was carried out during the standard 60–63-hour period after CIDR removal. The dose of semen used was estimated to be about 20 million live sperm.

After insemination, the hinds were held for 10 days in a paddock without a stag. They were then allowed to join a natural breeding group.

Conception was detected by ultrasonography in the period 45–64 days post insemination. However, the identity of the sire of each calf born to any hind that was inseminated was confirmed by DNA parentage testing.

Results

One hind was raddled within 15 hours of CIDR removal in 2 consecutive years. In year 1, it conceived to AI at 61 hours post CIDR removal despite having no detectable mucus in the vagina. In ten cases (21%) hinds were raddled between 39 and 46 hours after CIDR removal. In 30 cases (64%) hinds were raddled between 46 and 58 hours of CIDR removal. A total of five (11%) different hinds (one in year 1, two in each other year) showed no evidence of raddling.

When examined, four of the hinds that lacked raddle marks showed no evidence of ovulation. The fifth one had good uterine tone and moderate amounts of cervical mucus. The animal was inseminated and conceived.

Overall conception, as judged by ultrasonogram data was 74%. In year 1, 9 of 11 bred hinds conceived to AI, three of the conceptions being twin pregnancies. In year 2, 11 of 14 bred hinds conceived, three of these being twin conceptions. In year 3, 11 of 17 hinds conceived, one being a twin. Of the seven double conceptions, only two came to term as twins, another as a single calf. Of these two twin sets, one involved live female calves of 17 kg and 11.5 kg. The other twin pair of opposite sexes were born dead after they became trapped in the vagina together and were only discovered at 4:30 A.M. Delivery was assisted. The other four animals that had had twin conceptions did not carry to term.

Directly related to the pre-parturient losses seen in twin conceptions, the calving rate fell to 64%. DNA parentage testing revealed a mean gestation length of 247±5 days.

Discussion

Not only is the detection of estrus in wapiti difficult and time consuming, but the use of raddle harnesses and other paint marking devices as used in the sheep and cattle industries has proved to be unsatisfactory. This may be due to the near vertical position taken by the stag at time of copulation and hence its failure to exert any downward pressure on the hind.¹ However, during precopulatory low mounts, which are not always seen, there is considerable pressure exerted. The failure of conventional heat detecting devices may also be due to the fact that the heavy winter coat of wapiti, which is fully grown in by the advent of the breeding season, does not take raddle paints or chalk markers very well.

The conception rates achieved are a reflection of the average results obtained across North America (Bringans personal communication). Best results have been as high as 100% conceptions in groups of up to 20 hinds.

It has been shown that during a period from 40–60 days after breeding measurement of fetal size and other features of the pregnant uterus can be used to accurately predict conception date within less than 2 days.² The 10-day window, therefore, offers reasonable certainty of expected calving dates.

DNA data banks of specific named sires now exist in several laboratories in North America and New Zealand so that parentage confirmation is becoming more widely used in sales, both for buyer satisfaction and in some cases jurisdictional confirmation of purity.

The dose of PMSG was reduced in each of the three successive years of the program in order to try and counteract the unwanted incidence of twinning. Twinning is rare in wapiti and generally considered to be <0.5%.^1,3 However, there are instances of exceptionally high incidence of natural twinning on some wapiti farms (Bergen personal communication). There is a potential for freemartinism in different sex twins,⁴ but the risk does not appear to be great (Bergen personal communication).

In the one pair of live-born twins seen in this study, one animal was markedly lighter than the other. Normal birth weights for single wapiti calves are about 18 kg.¹ Calves born under 11.4 kg in weight have a less than 50% chance of survival, and calf weight at birth has a direct relationship with weight at 4 weeks and at weaning.^1,5 The smaller twin was successfully artificially reared.

The fact that four animals did not carry to term can be considered a distinct disadvantage from a commercial standpoint. One of these hinds was culled after remaining barren for 2 years.

Literature Cited

1.  Haigh, J.C. and R.J. Hudson. 1993. Farming Wapiti and Red Deer. Mosby, St. Louis, MO. 369.

2.  Revol, B. and P.R. Wilson. 1990. Rectal ultrasonographic pregnancy diagnosis and foetal aging of red deer. Massey University, Palmerston North, New Zealand. 133.

3.  Sadlier, R.M.F.S. 1987. Reproduction of female cervids. In: Wemmer, C.M. (ed). Biology and Management of the Cervidae. 123–144.

4.  Stewart-Scott, I.A., P.D. Pearce, G.H. Moore, and P.F. Fennessy. 1990. Freemartinism in red deer (Cervus elaphus L.). Cytogenet Cell Genet. 54:58–49.

5.  Thorne, E.T., R.E. Dean, and W.G. Hepworth. 1976. Nutrition during gestation in relation to successful reproduction in elk. J Wildl Manage. 40:330–335.