Rabbit semen collection and use.
Keywords: rabbit, semen, collection, vagina, artificial, lagomorph
Compared with Europe, Asia and South America, rabbit farming is underdeveloped in North America. Therefore, it is only superficially addressed in most of our animal science and veterinary curricula. Nevertheless, rabbits are important as livestock; farmed for meat and of course, angora fiber. They also have unique value for humane scientific study (See: Foote and Carney, 2000).
On one occasion, guided by ignorance, the author built this surprisingly effective artificial vagina (AV) to collect rabbit semen. It was based on a bovine AV but had a liner constructed from the finger of a surgical glove. A small hole on the side, covered by another piece of the glove was created to admit warm water and air as required. As can be seen, the liner terminated in a small collection vessel, cut from the conical tip of plastic test tube.
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Using a receptive doe, the process of semen collection was simple. Semen collection can be further simplified by training the buck to mount the skin of a doe, covering the hand that holds the AV. Copulation is rapid, resembling most closely, that seen in ruminants.
In the majority (~70%) of semen samples, a small plug of clear mucus will be found in the AV as shown below. This is a product of the vesicular glands. In sequential samples collected on the same day, the presence of a mucous plug is less likely (~5%). It was once surmised that the plug formed by this gel was essential to prevent loss of semen and produce normal conception rates. However it is now clear that conception rates can be excellent in the absence of any gel plug. Indeed, extended semen contains virtually no gel and conception rates using A.I. can be excellent. Therefore the presence of gel in rabbit ejaculates remains an enigma, rather like the gel in a stallion's ejaculate.
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To the author's eye, rabbit semen bears a striking resemblance to that of a bull; its motility and morphology being similar. Concentration is lower that of a bull's ejaculate however (~500 million per ml vs. 1000 million per ml). Nevertheless, wave motion (a function of both motility and concentration) can often be seen in rabbit ejaculates.
Puberty in males is reached at six to seven months of age but peak sperm production may not be reached until 2 years of age or more. At maturity, the volume of an ejaculate varies from 0.5 to 2 ml (occasionally more) but there is some variation at both upper and lower limits, partly due to significant volumes remaining on the liner of the AV. For that reason, the AV is sometimes flushed after collection to retrieve more of the ejaculate.
Although sperm production increases under the effect of increasing day length in wild lagamorphs, this effect is not generally noticeable in domestic rabbits.
Although AVs are commercially available, readers may be interested to read about an alternative AV (Bredderman, 1964) that can be built for small scale breeding. Semen extenders and insemination pipettes are widely available for commercial rabbit production. Sources are readily available on the Internet.
Handling and insemination
Although acceptable fertility has been reported with doses as low as 0.5 million sperm, common practice dictates that between 20 and 40 million sperm are used per insemination, aiming for no more than 0.5 ml in volume to reduce sperm loss after insemination. A single ejaculate therefore, may provide between 20 and 50 insemination doses.
For commercial use, semen from several males is pooled before insemination. The insemination pipette is bent dorsally to accommodate the ventrally-directed vagina and semen is simply deposited in the cranial vagina. No attempt is made to inseminate intra-cervically in either of the two cervixes.
Frozen-thawed semen is seldom used in commercial rabbit production. Instead, ejaculates are diluted in commercial diluents, cooled to between 18 and 20 deg.C and used over a 24 to 48 hour period.
To ensure that ovulation occurs (bearing in mind that it is predominantly mounting and not vaginal stimulation that induces ovulation in rabbits; Cf. cats) it is common to inject small intramuscular doses of GnRH analogs into the doe at the time of insemination. Because GnRH and its analogs are small molecules and readily absorbed through mucous membranes, some success has been achieved by adding GnRH analogs (usually buserelin) to insemination doses to induce ovulation. Without GnRH stimulation, the number of kits per litter is not commercially viable.
Selected references:
Alvarino, J.M.R. 2000. Reproductive performance of male rabbits World Rabbit Science Association, Volume 8, supplement 1. pp.13-35
Amann, R.P. 1966. Effect of ejaculation frequency and breed on semen characteristics and sperm output of rabbits. J. Reprod Fert. 11:291-293
Bredderman, P.J. 1964. An improved artificial vagina for collecting rabbit semen. J. Reprod. Fert. 7:401-403.
Brun, J.M. et al 2002. The relationship between rabbit semen characteristics and reproductive performance after artificial insemination. Anim. Reprod. Sci 70:139-149
Foote, R.H. and Carney E.W. 2000.The rabbit as a model for reproductive and developmental toxicity studies
International rabbit reproduction group. 2005.Guideline for the handling of rabbit bucks and semen. World rabbit.Sci. 13:71-91
Lavara, R. et al. 2005. Do parameters of seminal quality correlate with the results of on-farm inseminations in rabbits? Theriogenology 64:1130–1141
Mocéa, E. and Vicenteb, J, 2009. Rabbit sperm cryopreservation: A review. Animal Reprod Sci. 110: 1–24
Morell, J.M. 1995. Artificial insemination in rabbits. British Vet. J. 151: 477-487
Mukherjee, D.P. et al 1951.The Gelatinous Mass in Rabbit Semen Nature 168: 422 - 423
Theau-Clément, M. 2016. Relationships between rabbit semen characteristics and fertilising ability after insemination. Animal. 10:426-431
Vincente, J.S. et al. 2008. Rabbit reproductive performance after insemination with buserelin acetate extender. Livestock Science 115: 153–157
Viudes-de-Castro, M.P.Ovulation induced by mucosa vaginal absorption of buserelin and triptorelin in rabbit 68: 1031-1036. Theriogenology 68: 1031–1036
http://placentation.ucsd.edu/rabbitfs.htm Kurt Benirschke.
