Artificial insemination in canids: A useful tool in breeding and conservation

Abstract

Artificial insemination (AI) and semen freezing have become services available to dog owners worldwide, and the demand for services to freeze semen is increasing. In other canids such as the fox, the fur industry utilizes fresh or frozen semen to artificially inseminate vixens to produce pelts. Clearly, AI facilitates the use of a male to sire several females by diluting the ejaculate, increases breeding hygiene, and allows crossing between species with slightly different breeding seasons. The African wild dog (Lycaon pictus) is currently considered by the World Conservation Union (IUCN) as one of most endangered canids. In captive populations of African wild dogs, semen has been frozen with encouraging results, using a standard cryopreservation protocol for domestic dogs, but successful AI has not been reported. In wolves, there is one report regarding the live birth of an offspring after intravaginal AI of a deslorelin-induced estrous female. In 2005, three Mexican gray wolf females were artificially bred by intrauterine insemination with freshly collected semen from unrelated males, and all females whelped. Artificial insemination may be vaginal, intrauterine or intratubal, and the semen may be fresh, fresh and chilled (diluted), or frozen–thawed, and the source of semen may be epididymal or ejaculated. In the domestic dog, the results are good to excellent for AI with all three types of processed semen when the source is ejaculated semen, whereas epididymal sperm still yields poorer results. Species differences in female physiology, as well as differences in the cryotolerance of the sperm from various canid species, warrant further research and development.

Introduction

Artificial insemination and semen freezing are available to dog owners worldwide, and the demand for semen freezing during large international dog shows is increasing. Semen from dogs originating from continental Europe, as well as the Americas and Australia, was cryopreserved during the 2008 World Dog Show in Stockholm, Sweden, to be used to artificially inseminate bitches in Scandinavia at a later date. Interested breeders in the UK purchase semen from UK dogs exported to Scandinavia, whose semen had been cryopreserved and kept frozen for a number of years, to ‘get their breeding lines back’. Field trial and competition dogs are watched and evaluated in their home countries by traveling breeders, and semen from these elite dogs are requested to import superior working stock. In the guide dog services for the blind and in the military, customs and police (odor detection) dogs are becoming an enterprise worldwide, and semen from valuable sires are requested to minimize costs of keeping or transporting live animals. Fresh, chilled semen is increasing as an alternative to mating or use for AI with frozen semen when time is short (e.g. the female is already in estrus) and transport distances are not too far. New commercial diluents for fresh semen are being developed that may enable storage of chilled semen for several days, which eliminates transport distance as an obstacle to AI with fresh semen [1].

In other canids, such as the fox, the fur industry utilizes fresh or frozen semen to artificially inseminate vixens to produce pelts. In 2007, 65,000 female foxes in Norway were inseminated with fresh semen, and approximately 80% of the 155,000 marketed pelts were produced from AI offspring (2007 records of the Norwegian Fur Breeders’ Association). In The International Fur Trade Federation’s state of the industry report for 2007, it was stated that worldwide sales figures for all fur clothing rose to $15 billion in 2007 (up by 11% in 2006 [2]). Foxes constitute a substantial part of the fur-farmed species. Both farmed species, the red fox and its color variants (Vulpes vulpes) and the blue fox (Alopex lagopus) are also bred naturally, but AI facilitates the use of a male for several females by semen dilution, increases breeding hygiene, and allows crossing between the two species, which have a slightly different breeding season.

The African wild dog (Lycaon pictus) is currently considered by the World Conservation Union (IUCN) as one of most endangered canids in the world [3]. Implementation of assisted breeding in the captive African wild dog is restricted by a lack of knowledge regarding their reproductive physiology and the apparent difficulty of manipulating the complex social dynamic of the pack in order to conduct reproductive procedures. In captive populations of African wild dogs, semen has been frozen with encouraging results using a standard cryopreservation protocol for domestic dogs [4], [5]. So far, however, there are no reports of live offspring as a result of AI.

Several wolf species around the world are threatened by inbreeding and by human intervention. In addition to protecting the animals from poaching and securing their habitats, artificial breeding techniques may be one of several solutions to exchange genetic material between wild or captive populations. In wolves (Canis lupus spp.), there are reports regarding sampling and cryopreservation of semen from, for example, the subspecies gray wolf (Canis lupus), red wolf (Canis rufus) [6], [7], and Mexican gray wolf (Canis lupus bayleyi) [8]. One account of live birth offspring after intravaginal AI of one female wolf inseminated in a deslorelin-induced estrus is reported in the scientific literature [9]. In 2005, the first author of the current review was involved in cooperation with the AZA Wildlife Contraception Center at the St. Louis Zoo (St. Louis, MO, USA) in an effort to carry out non-surgical intrauterine AI of female Mexican gray wolves in spontaneous estrus. In February 2005, three Mexican gray wolf females were artificially inseminated with freshly collected semen from unrelated males (Fig. 1). All females whelped. The experiment attracted media interest and was cited in an article by the New York Times. One successful pregnancy following insemination with frozen semen was reported in the gray wolf (Canis lupus) by Seager and his group [10].

The objective of this review is a state of the art survey of the techniques used for AI, and results and challenges we meet when applying AI to canid species for breeding or conservation purposes.