In vitro embryo production in cattle

[摘要] 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 implyinganimals that could neither reproduce nor produce embryos through conventional MOETprocedures due to old age, pregnancy, repeated MOET procedure treatments, certainabnormal uterine conditions and general failure to conceive and become pregnant followingrepeated inseminations or natural services, as well as due to physical injuries.The investigation concentrated on whether it was possible to produce embryos from a donorcow with this profile and additionally other aspects such as - the best logistical approach forIVEP when presented with a fertility-impaired donor cow - whether superovulation could beused as an enhancing tool when presented with a pregnant donor - and the affect of seasonon all aspects of IVEP from fertility-impaired donor cows.It was established that a period of OPU could enhance the production of higher numbers ofembryos additional to eventual slaughter of the donor cow (10 more embryos on average perdonor) and that the culturing of a small number of oocytes and embryos does not negativelyaffect 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 withthese types of donor cows and it also suits the practical situation faced when producing invitro embryos from small numbers of oocytes collected from these donor cows.It was evident that additional superovulation does not enhance the IVEP potential of pregnantdairy cows (0.02 more embryos per donor per OPU session), unless more refined research isundertaken to optimize the actual superovulation protocols and oocyte recovery procedures.The additional cost implication of added hormonal treatment for superovulation may actuallyact as a deterrent for cattle stud breeders to embrace this technology. However, the merefact that it was possible to produce embryos from pregnant dairy cows could be utilized as auseful tool for accelerated genetic improvement in the dairy and beef cattle industry in SouthAfrica.It was established that season (recorded as ambient temperature and photoperiod) had adefinite effect on all aspects of IVEP in fertility-impaired beef cattle cows, a trend that wasevident from literature in some laboratory IVEP trials on slaughterhouse material and also inthe normal reproduction pattern of beef cattle cows in the South African context. This trendmanifested itself in the IVEP pattern of fertility-impaired cows. There was a definite decreasein IVEP during the period of late summer (5.4 %) and early autumn (0 %) with a definitedelayed effect of high temperatures and possibly photoperiod evident. Alternatively, theoptimum 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 photoperiodaffect. This effect on oocyte quality and eventual embryo production results could also serveas an indicator for other management decisions regarding normal reproduction managementin beef cattle as well as the planning of conventional superovulation and embryo transferprogrammes.From the obtained results it was clear that IVEP is possible from fertility-impaired andpregnant donor cows. However, there are certain aspects that need to be focussed on toensure that optimum results are obtained when applying IVEP on these animals. Optimumresults 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 cattleindustry and is not within the ability of all breeders. This will, however, become a powerfultool for use in accelerated genetic improvement programmes and will also ensure thatsuperior genetic material from animals that would have been lost for breeding will continue tobe utilized in the cattle breeding industry.

[发布机构] University of the Free State