In vitro embryo production in cattle

English: The objective of this study was the development of efficient in vitro embryo production (IVEP) technology for application on fertility-impaired beef and dairy cows. Fertility-impaired implying animals that could neither reproduce nor produce embryos through conventional MOET procedures due to old age, pregnancy, repeated MOET procedure treatments, certain abnormal uterine conditions and general failure to conceive and become pregnant following repeated inseminations or natural services, as well as due to physical injuries. The investigation concentrated on whether it was possible to produce embryos from a donor cow with this profile and additionally other aspects such as - the best logistical approach for IVEP when presented with a fertility-impaired donor cow - whether superovulation could be used as an enhancing tool when presented with a pregnant donor - and the affect of season on all aspects of IVEP from fertility-impaired donor cows. It was established that a period of OPU could enhance the production of higher numbers of embryos additional to eventual slaughter of the donor cow (10 more embryos on average per donor) and that the culturing of a small number of oocytes and embryos does not negatively affect the eventual IVEP result (10 % more embryos were produced from individual donors). result was a good indicator of how to plan the logistical approach when confronted with these types of donor cows and it also suits the practical situation faced when producing in vitro embryos from small numbers of oocytes collected from these donor cows. It was evident that additional superovulation does not enhance the IVEP potential of pregnant dairy cows (0.02 more embryos per donor per OPU session), unless more refined research is undertaken to optimize the actual superovulation protocols and oocyte recovery procedures. The additional cost implication of added hormonal treatment for superovulation may actually act as a deterrent for cattle stud breeders to embrace this technology. However, the mere fact that it was possible to produce embryos from pregnant dairy cows could be utilized as a useful tool for accelerated genetic improvement in the dairy and beef cattle industry in South Africa. It was established that season (recorded as ambient temperature and photoperiod) had a definite effect on all aspects of IVEP in fertility-impaired beef cattle cows, a trend that was evident from literature in some laboratory IVEP trials on slaughterhouse material and also in the normal reproduction pattern of beef cattle cows in the South African context. This trend manifested itself in the IVEP pattern of fertility-impaired cows. There was a definite decrease in IVEP during the period of late summer (5.4 %) and early autumn (0 %) with a definite delayed effect of high temperatures and possibly photoperiod evident. Alternatively, the optimum period for IVEP seemed to be during winter (between 11 % and 20 %) and spring (between 22 % and 26 %) which also indicated a possible temperature and photoperiod affect. This effect on oocyte quality and eventual embryo production results could also serve as an indicator for other management decisions regarding normal reproduction management in beef cattle as well as the planning of conventional superovulation and embryo transfer programmes. From the obtained results it was clear that IVEP is possible from fertility-impaired and pregnant donor cows. However, there are certain aspects that need to be focussed on to ensure that optimum results are obtained when applying IVEP on these animals. Optimum results are a prerequisite for this technology to be accepted by the South African cattle breeding industry. IVEP is still in a preliminary phase of application in the South African cattle industry and is not within the ability of all breeders. This will, however, become a powerful tool for use in accelerated genetic improvement programmes and will also ensure that superior genetic material from animals that would have been lost for breeding will continue to be utilized in the cattle breeding industry.