BRITISH COLUMBIA GOAT ASSOCIATION
British Columbia Goat Association
Dr. Brian W. McOnie, Creekside Animal Clinic Ltd. Vernon BC
Embryo transfer (ET) is a recognized reproductive technology in food-animal production. It allows genetically superior females to make greater contributions to breeding programs. Also, appropriate processing of embryos recovered from animals infected with chronic viral and bacterial infections means those embryos can be transferred to healthy recipients with virtually no risk of disease transmission. Recovered embryos can be frozen for transfer at a future time or different location. The sale of embryos obtained from valuable donors represents an income stream for while breeders can retain ownership of their valuable donors.
The small size of goats has limited the routine commercial application of ET to surgical procedures. Although surgical ET is successful when performed by skilled and experienced practitioners, several factors have discouraged its widespread adoption, especially in dairy goats. Surgical ET implies risks with anesthesia and surgery. It requires specific equipment, training and expertise. Many dairy goat breeders have not taken advantage of the benefits of ET due to their perception of these risks.
Transcervical embryo recovery offers an alternative to conventional surgical embryo recovery. It should be repeatable several times during the breeding season, may be performed with only light (if any) sedation, is minimally invasive and humane and avoids the potential complications associated with anesthesia and surgery. It should offer breeders many of the benefits of ET with minimal risk.
Transcervical embryo collection has been performed under laboratory conditions with Boer and dairy goats but clinical trials under commercial situations are not reported. Drawing upon experience gained through almost 20 years of surgical ET at our practice, a trial was undertaken in British Columbia to assess the potential for transcervical embryo recovery from dairy goats under comercial conditions.
The donors had kidded previously and were considered to be free of reproductive disorders at the beginning of the study. Each doe underwent superovulation to increase the number of eggs (ova) available for release at the time of breeding. The donors were mated to bucks of proven fertility and embryo recovery procedures were performed 6.5 days later. Does in which transcervical embryo recovery could not be performed underwent surgical embryo recovery. Laparoscopy (insertion of a rigid fibre-optic scope into the abdomen) was performed to determine the number of embryos that might be expected based on a count of the number of sites where ovulations had occurred.
In 17 of 28 (61%) attempts it was possible to pass a transcervical catheter. Numerically (but not statistically significant) fewer total embryos and ova were recovered on average transcervically (5.94) than were recovered surgically (12). There was no statistically significant difference between the number of IETS grade 1 and 2 embryos recovered transcervically (3.47) and surgically (6.67). All grade 1 and 2 embryos were frozen for subsequent study.
Five of 10 (50%) donors from which viable embryos were recovered yielded one to three grade 1 and 2 embryos. One doe responded with 23 grade 1 and 2 embryos. The response to superovulation (measured by CL counts) tended to be greater in April than in January or November. This indicates that superovulation of dairy goats in BC in April can be successful. The efficiency of embryo recovery (total embryos and ova relative to CL count) was consistent through the trial period. The average number of embryos was lowered in that does which had not responded to superovulation were included in the trial. The efficiency of this procedure could be enhanced by identifying females which have failed to respond to superovulation and not submitting them for embryo collection.
The full report will be available shortly and a video of the procedure is on Youtube at http://www.youtube.com/watch?v=FEsKxt-NVT8