Embryo transfer in cattle
Cows can now produce many offspring in a single year using multiple ovulation and embryo transfer technology. Despite its obvious benefits embryo transfer is not widespread in Kenya because of its high cost and being not readily available. Only a few individuals and big farms can afford this technology. However the demand is gradually increasing as more farmers want to improve productivity of their livestock.
Embryo transfer is a technique where a fertilized embryo from a donor female is transferred to another female which then carries the embryo to the end of pregnancy. Any breed of cattle can be used as surrogate mother and this allows farmers to use even poor quality breeds to produce high quality livestock.
The donor female is first prepared by being placed in anesthesia. Using antiseptic solution the perineum is scrubbed and cleaned before the process begins. There are two methods of embryo collection in cows, the surgical and non surgical method. In the surgical method a suitable flushing medium is flushed through the oviduct to the upper part of the uterine horn using a syringe and a blunt needle. The flushings are then collected through a small glass tube inserted into the uterine lumen. In the non surgical method the cervix is dilated using a cervical dilator to allow manual insertion of Foley’s catheter into the uterine horn. Using a suitable flushing medium the uterine horn is then irrigated. A plastic balloon is inflated to seal off the horn of the uterus. Embryos are flushed out with culture media and collected in petri dishes.
Using very powerful microscopes the embryos are screened for normalcy. The embryos should be normal morphologically, have six even blastomeres and no vacuoles, have no debris in the morula, and the cystoplasmic and nucleic material should not be fragmented. During this time of embryo selection the embryo can be manipulated for preservation, embryo splitting, embryo sexing, nuclear and gene transfer.
Farmers who intend to use the embryos must prepare the surrogate animals for implantation. The recipient should be sexually mature or a regular good breeder free from infection in the genital tract. If the cow has given birth then an allowance of 90 days post partum period is required. The cow should be recycling normally with good physical condition and not fat.
For successful embryo transfer in cows, synchronization of estrus between the stages of embryo in the donor and the stages of reproductive tract of the recipient is essential. The recipient should be on heat within 12 hours of the donor and this can be achieved through synchronization of estrus with that of the surrogate cow's hormonal cycles so that it can accept the new embryo.
Embryos can be transferred surgically or non-surgically. In surgical method laporotomy is done under local anaesthesia. The embryo is deposited in the uterine lumen through an incision in the uterine horn. The non-surgical method is the preferred method in cows and the embryo is deposited through the cervix into the uterus using an AI gun 6 days after estrus.
The average number of calves produced per super-ovulation is 3-4 calves. It is possible to induce a cow to super-ovulate for 4-5 times a year. 10 calves can be produced per cow per year.
At KSh 25,000 to 30,000 embryo transfer technology is still very expensive and out of reach to many farmers. However with quality heifers becoming scarce due to increasing demand, the development of embryo technology will go a long way in complementing the existing breeding efforts and provide additional incomes and incentives for farmers to increase use of superior genetics sourced from outside the country. The ADC Namandala farm in Kitale has been developing the breeding technology and has also been working on a quarantine facility for semen and embryo extraction at the ADC Mutara ranch in Laikipia. Other players include the International Livestock Research Institute (ILRI), Central Artificial Insemination Station and Kenya Livestock Breeders Organization under the umbrella body of East Africa Semen and Embryo Transfer Association.
Kenyan livestock farmers can also export embryos and participate in international trade in genetic products. Embryo Plus in collaboration with the Kenya Boran Cattle Breeders Society (BCBS) has been collecting embryos from Boran donor cows in Kenya and exporting to South Africa in the last 5 years.