Embryo transfer in Bos indicus cattle.

In the present short review superovulation treatments commonly used for Bos taurus and/or Bos indicus will be addressed with emphasis in recent superstimulation protocols associated with pharmacological manipulation of the follicular dynamics to improve donor management and potentially embryo yield. Results obtained after superovulation treatments in which the time of LH surge is selectively delayed as an attempt to improve embryo yield are presented and discussed.     

Embryo transfer from donor cattle persistently infected with bovine viral diarrhea virus

This study was done to examine the reproductive efficiency of embryo transfer donors that were persistently infected with bovine viral diarrhea virus (BVDV) and to determine the potential for vertical or horizontal transmission of BVDV during embryo transfer from persistently infected donors. The reproductive inefficiency of 7 different persistently infected donors was evident by consistent failure at superovulation and/or fertilization. Washing of embryos according to the reccommendations of the International Embryo Transfer Society (IETS) prevented the adherence of BVDV to embryos and to unfertile and degenerated ova, as determined by virus isolation and polymerase chain reaction (PCR) assay. In addition, a normal, BVDV antibody seronegative and BVDV-negative calf was born following transfer from a PI donor to a seronegative recipient.     

Embryo transfer in two-year-old donor mares

Embryos were collected from two-year-old donor mares and transferred surgically during 1983 and 1984. The overall embryo recovery rate from two-year-old donors was 36.3%. Over both years, 71.4% of the donors ($\text{30}\text{42}$) provided at least one embryo. There was a trend both years for slightly higher embryo recovery rates prior to August 1 (47.7%), as compared to after August 1 (31.1%). Pregnancy rates in recipient mares after surgical embryo transfer were not affected by month of the breeding season. However, there was a trend for improved pregnancy rates when embryos were transferred after August 1 (87.5%), as compared to before August 1 (70.0%). There was a 8.3% incidence of fetal loss between Days 15 and 35 of gestation in recipients. The incidence of fetal loss between Days 35 and 60 of gestation was 2.7%. Based on these data, the chance of obtaining a pregnancy from a two-year-old mare is 28.2% (36.3% recovery × 77.7% pregnancy rate). Thus embryo transfer may prove to be a beneficial tool for obtaining foals from two-year-old donor mares.     

Embryo transfer in the dog and cat

The practicality and feasibility of embryo transfer technology in dogs and cats is quickly becoming a clinical reality. Although progress has been slow, I anticipate that embryo transfer will be a practical and an economical technique in the near future. Most importantly, it is essential that the practical lessons learned with equine and bovine embryo transfer be integrated into the development of canine and feline programs.     

Embryo transfer in fertile and infertile cows

Pregnancy rates were compared between fertile and infertile donors in an embryo transfer program. Non-surgical embryo transfer techniques were utilized for examination of uterine contents and collection of ova. Recovered embryos were transferred surgically into suitable recipients. Three groups of donors were included in this investigation: a) fertile; b) infertile, due to known causes (diagnosed); c) infertile, due to unknown causes (undiagnosed). There were 11.3, 6.6 and 8.0 corpora lutea; 6.8, 1.2 and 1.0 fertilized ova; 3.6, 0.8 and 0.4 pregnancies per superovulation for the fertile, diagnosed and undiagnosed groups, respectively. In 23 months, unsuperovulated, fertile, diagnosed and undiagnosed donors yielded 17, 15 and 9 fertilized ova which resulted in 15, 13, and 3 pregnancies, respectively. Donors treated for uterine infections, adhesions or cystic ovaries prior to superovulation responded with 10.1, 7.6 and 4.1 corpora lutea; 1.9, 4.0 and 0.3 fertilized ova; 1.1, 3.3 and 0.2 pregnancies per superovulation, respectively. Relatively few viable embryos were recovered from donors with chronic cystic ovaries or from infertile cows of unknown etiology. Infertile donors, when compared to fertile donors, were unproductive when used for embryo transfer.     

Embryo transfer in domestic South American camelids

Intraspecific and interspecific embryo transfer in domestic South American camelids is developing into a well-established technique. Reports reveal many benefits of using reproductive biotechnologies to allow rapid propagation of alpacas and llamas of high genetic merit (e.g., high fiber quality, preserve color variation). The objective of this review is to provide up-to-date information about embryo transfer in domestic South American camelids. Specific information is provided on criteria for male selection, donor and recipient synchronization, the practice of single- vs. super-ovulation protocols, embryo recovery and transfer techniques, advances in cryopreservation of embryos, results of intra- and inter-specific transfer, and the future of the embryo transfer in domestic South American camelids.