Studies on the establishment of pregnancy in the ewe
Novel laparoscopic techniques were developed for intrauterine insemination, embryo recovery and embryo transfer in ewes. For the intrauterine insemination technique the use of 48 x 106 freshly collected spermatozoa per ewe (2% of that used in natural service) gave ovum fertilization rates in superovulated ewes that consistently exceeded 90%; for frozen-thawed semen the fertilization rate was 55%. The use of the technique at 28 days following parturition, to bypass the involuting uterus with fresh semen, gave a fertilization rate of 80%. For the recovery of ova two catheters were used in a through-flush procedure. This gave recovery rates of 35, 76 and 66% for ewes flushed on three consecutive occasions spanning a two-month period and resulted in no detriment to subsequent fertility. The laparoscopic transfer of 42 uterine-stage embyros to 21 synchronised recipient ewes gave a pregnancy rate of 76%. In the first of two embryo transfer experiments to separate the effects of pre- and post-mating nutrition on embryo survival and the growth of the conceptus, 123 embryos collected from ewes maintained on a standard nutritional regime were transferred to 63 recipient ewes that varied widely in body condition and plane of nutrition. At slaughter on day 60, fifty-eight (92%) of the ewes were pregnant with 100 (81%) foetuses. There was no effect of nutritional status on embryo survival but foetal weight varied with body condition, plane of nutrition and plasma glucose. In the second experiment 99 embryos recovered from ewes of widely-varying nutritional status were transferred to 51 uniformly-maintained recipients. At slaughter (60 days) forty-eight (94%) were found to be pregnant with 82 (83%) viable foetuses. Embryo quality varied with body condition and plasma glucose but embryo survival after transfer was independent of the nutritional status of the donor. In contrast there were carry-over effects of donor nutrition of foetal growth.