Semen Freezing And Subsequent Insemination In Angora GoatsThursday, 3rd June 2021
By Dr Mackie Hobson
SEMEN FREEZING AND SUBSEQUENT INSEMINATION IN ANGORA GOATS
Genetic improvement in a breed is dependent on the rate of genetic change achieved in stud animals. By making superior genetics available to the entire industry through frozen semen would speed up the rate of genetic change.
Gretha Snyman (Grootfontein) and Frans Jooste (GeneCo) develop a frozen semen protocol for South African Angora goats.
PREPARATION OF RAMS FOR SEMEN COLLECTION
Preparation of rams for semen collection for freezing should start at least eight weeks beforehand to ensure optimum spermatozoa production during collection.
Good nutrition with Zinc, Selenium, Vitamin E and Vitamin A supplementation is essential during the pre-collection period. Rams should be fed this diet at 2-3% of their body weight. Lucerne hay should also be provided at 500 g/ram/day.
Rams should be exercised daily. The aim is to have rams in a body condition (BCS) score between 3 and 4 out of 5. The rams could be exposed to mature synchronised ewes for four weeks before semen collection. Photoperiod plays a role in the quality and quantity of spermatozoa produced. Therefore, the normal autumn breeding season for Angora goats is preferable.
PREPARATION OF EWES BEFORE ARTIFICIAL INSEMINATION
Ewes should have a body condition score (BCS) of at least 2.5 on a scale-out of 5, six weeks before artificial insemination. From six weeks before the date of artificial insemination, ewes need to be on a rising plane of nutrition, and the BCS should increase. On natural pasture of the Karoo and Eastern Cape, ewes should receive 200 to 500 grams of a production lick daily, depending on the BCS at the start of the program. Good quality roughage must be available at all times.
For an artificial insemination program, it is preferable to use ewes that have kidded at least once and to avoid using ewes older than 7 years of age
A recommended 17-day (traditional protocol) and 9-day (short protocol) synchronisation programs for ewes for trans-cervical insemination with fresh semen and laparoscopic insemination with frozen-thawed semen are summarised in the tables below.
- 17-day protocol (traditional protocol)
9- day protocol
SEMEN FREEZING PROTOCOLS
Semen was frozen according to various protocols in either pellets or straws. Post-thaw motility rates above 50% can be achieved with the straw-freezing protocols followed since 2013.
It is recommended that at least 20 million progressively motile spermatozoa be placed in the uterus by laparoscopic insemination or 100 million progressively motile spermatozoa by trans-cervical insemination.
It is well known that there is a large variation in semen quality traits and freezability among individuals.
In general, trans-cervical insemination with either fresh or frozen semen did not yield acceptable results. Although laparoscopic insemination with frozen-thawed semen produced better results than with fresh semen, variable results were obtained in the different years. As far as specific aspects are concerned, from the results of the 2016-trial at Grootfontein, it is clear that the shorter 9-day synchronisation cycle yielded better conception results when using CIDRs in Angora goats than the longer 17-day cycle.
Results indicate that it is possible to obtain acceptable conception rates with laparoscopic insemination with frozen-thawed semen when following the prescribed protocols.
Average 47.8% conception rates = Laparoscopic insemination
The results obtained with the current study are slightly lower than those reported in the literature for goats and sheep.
The quality of fresh semen of Angora rams should not pose a problem during the freezing process of semen. However, differences among rams do exist. A workable protocol for the freezing of semen in straws is available that can yield acceptable conception rates with laparoscopic insemination. It should be kept in mind that the preparation and management of the ewes play an important role in the success of this protocol.
Wide variation in conception rates was achieved with frozen-thawed semen during these trials. Results varied from excellent to poor. Further research and trials should focus on eliminating this variation Timing of ovulation, failure of fertilisation, or incorrect insemination dose could be factors contributing to the variation observed and should be investigated.
Extracted from: SEMEN FREEZING AND SUBSEQUENT INSEMINATION RESULTS IN SOUTH AFRICAN ANGORA GOATS M.A. Snyman & F. Jooste (Grootfontein Agricultural Development Institute) and GeneCo, Small Stock Reproduction Centre.