Embryo transplantation in cattle. Non-surgical recovery of embryos from repeat breeders
Greve, T.
Acta Veterinaria Scandinavica 21(1): 26-33
1980
ISSN/ISBN: 0044-605X PMID: 7386328 Document Number: 162833
Fourteen true repeat breeders with entirely normal estrous cyclicity > 1 yr after calving and 14 control donor cows were superovulated with pregnant mare serum gonadotropin (2000 IU) and flushed non-surgically 6-8 days after the superovulatory heat. The superovulatory response was identical for the 2 groups such as assessed by the number of corpora lutea [CL] (9.4 .+-. 1.8 CL/repeat breeder and 9.1 .+-. 1.5/control cow), occurrence of ovarian overstimulation (polycysts), presence of a non-countable amount of CL, negative outcome of the flushings and the number of recovered embryos (5.8 .+-. 1.0 embryos/repeat breeder and 6.0 .+-. 1.8 embryos/control cow). The most pronounced difference between the 2 categories of animals was related to the fertilization rate of embryos. In the repeat breeder group only 2.4 embryos/cow or 41% were fertilized, while the control animals attained a fertilization rate of 4.9 embryos or 82%. Since most factors liable to interfere with the fertilization process were identical for both groups (age, breed, nutritional and management conditions, semen quality, dose, artificial insemination-technician), it is believed that intraovarian, follicular, or follicular-dynamic conditions were responsible for producing a high proportion of non-fertilizable oocytes.