FACTORS AFFECTING SUCCESS OF EMBRYO COLLECTION AND TRANSFER IN A TRANSGENIC GOAT PROGRAM

During a goat transgenic program that took place in Israel from July 1 995 to February 1996, Saanen (n = 343) and Nubian x Damascus (n = 378) crossbred goats of mixed ages were used as donors (n = 433) and recip ients (n = 288). The effects of season, age, number of surgical proced ures, previous hormonal treatments and ovulation rate on the number of microinjectable embryos collected were studied. Likewise, the effects of these parameters on the pregnancy rate as well as the number of em bryos transplanted, endogenous progesterone concentrations and exogeno us progesterone supplementation were studied in recipient does. Follow ing superovulation with ovine follicle stimulating hormone, 85% of the does responded with 13.6 +/- 5.7 (mean +/- SD) ovulations/doe. Age, m onth and number of previous hormonal treatments significantly affected the ovulation rate. The average recovery rate was 70%, and it was aff ected only by the ovulation rate. Pronuclei were visualized in about 3 0% of the flushed embryos (including unfertilized ova), and those were microinjected with human serum albumin gene construct. About 68% of t he injected embryos underwent at least one division during an overnigh t incubation, and those embryos were transferred, giving about 2.0 tra nsferred embryos per ovulated donor. Of the recipients, 86% responded following synchronization with 3.1 +/- 1.6 (mean +/- SD) ovulations pe r doe. Breed and month had a significant effect on the ovulation rate. Two or three microinjected embryos were transferred to each recipient , resulting in more than a 40% pregnancy rate during September to Nove mber. Lower pregnancy rates were obtained before and after that period . By monitoring plasma progesterone concentrations in the recipients i t was found that progesterone concentration was correlated with the ov ulation rate. However, the pregnancy rate was not affected by progeste rone concentration. During January and February, 30 to 50% of the reci pients failed to develop functional corpora lutea (CL) following embry o transfer, which explained the lower pregnancy rate in those months. Of the 86 kids born 4 were transgenic. (C) 1997 by Elsevier Science In c.