Rabbit ova were transferred to both sides of synchronous pseudopregnant recipients; on one side the ova were transferred to the ovarian bursa to assess the efficiency of ovum reception, and on the other side were deposited within the Fallopian tube to provide information on ovum transport. The recipients were treated with oestrogens, progesterone, or combinations of these hormones. Ova were also transferred to control untreated animals, and to those in which superovulation had been induced. Recipients were autopsied 4 days post coitum, and the ova recovered and examined.
Oestrogen treatment did not influence ovum reception, progesterone produced a slight improvement, and a combination of oestradiol and progesterone gave a greater improvement. Retention of ova in the Fallopian tube was induced by oestrogen treatment, and this effect was opposed when progesterone was given also. Survival rate of blastocysts was reduced by oestrogen treatment especially when ova were retained within the tube. Retained ova had thicker mucin coats. Fewest ova were lost from the reproductive tract in oestrogen-treated animals. Factors affecting rate of pre-implantation embryonic growth are discussed.
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