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C. E. ADAMS

Summary.

Morulae recovered from superovulated donors 60 hr post coitum were transferred to the uteri of recipients ('temporary' recipients) on Day 3, 5, 7, 9 or 11 of pseudopregnancy. The eggs were again re-covered either 6 hr or 24 hr after transfer and, following microscopic examination, re-transferred to the uteri of synchronous recipients in order to test viability.

The proportion of eggs recovered from the temporary recipients, 73 to 97% was little affected by the stage of pseudopregnancy, except for a slight decline on Day 11 compared with earlier stages. However, the reaction of the eggs, as judged after 24 hr, was markedly affected, varying from continued development (up to the early blastocyst stage) in the Day-3 or Day-5 uteri to degeneration in the most asynchronous uteri (Day 9 and Day 11).

The appearance of the eggs was strongly correlated with their ability to survive following re-transfer ; practically no eggs (3 out of 113) exposed for 24 hr to the Day-9 or Day-11 uteri survived to term. The associated low rates of pregnancy (failure of implantation) indicated that the eggs perished early (already dead at transfer, or dying shortly afterwards), which was confirmed by autopsy 3 or 4 days after transfer.

The injurious effect of the progestational uterus on the morula appeared to develop gradually; it was detectable in some does on the 7th day and expressed itself fully by the 9th to 11th days of pseudopregnancy. No specifically harmful factor or deficiency has been identified in such uteri in which stages earlier than the morula are also affected.

Morulae transferred to the oviduct on the 11th day of pseudopregnancy continued to develop with the majority reaching the early blastocyst stage. After 24 or 48 hr under such conditions, 56% and 27% proved fully viable when re-transferred.

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C. E. ADAMS

The mink has a short, well-defined breeding season extending from February to March. On fur farms in Great Britain, as in Scandinavia and North America, the first matings usually take place about 10th March. Various mating systems are employed, all of which tend to involve the use of the same or different males at intervals; for example, mating on Day 0 (male A), Day 1 (male B), and Days 8 and 9 (male C). Normally, ovulation is induced by the stimulus of coitus which it follows after 36 to 37 hr (Hansson, 1947) or after approximately 48 hr according to Enders (1952). Enders also reported that many females ovulated following only brief contact with a male during which the female was not seized nor intromission attempted.

Each breeding season, a proportion of females fail to mate: Enders estimated 10 to 30% but a recent survey (Ministry of Agriculture, Fisheries and

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C. E. ADAMS

Summary.

Fifty-four rabbits were inseminated intraperitoneally 3 to 6½ hr before the injection of hcg given to induce ovulation. From 0·3 to 1·0 ml of semen or epididymal spermatozoa, containing 10 to 390 × 106 spermatozoa was inseminated. Thirty-nine of the does were autopsied 17 to 44 hr after hcg. The proportion of eggs recovered varied from 28 to 95 % and was generally inversely related to that of eggs fertilized, which varied from 20 to 79 %, excluding eighteen does having practically no fertilization. Poor egg recovery and higher fertilization rates tended to be associated with larger numbers of spermatozoa inseminated. In fifteen does examined by laparotomy on Day 10, eight were pregnant with 28 to 36 % of the ovulations represented by implants, 68 % of which survived to term.

In twenty-five does, inseminated with 100 to 386 × 106 epididymal or ejaculated spermatozoa, 0, 10, 15 or 20 hr before giving hcg, 50 to 79 % of the eggs were fertilized, except in the 20-hr group where fertilization failed. Egg recovery improved, from 22 % to a maximum of 91 %, as the interval between insemination and ovulation was extended.

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C. E. ADAMS

Summary.

The fate of the unfertilized egg was studied in a total of forty-five pseudopregnant rabbits, examined at autopsy at 24-hr intervals between Days 5 and 15. Throughout this period, egg recovery failed in only three animals and upwards of 50% of the eggs expected were recovered from the majority. The first signs of degeneration affecting the vitellus were noted about Day 5 and the process became marked during Days 7 to 10.

In a further sixteen does in which either one or both oviducts were ligated shortly after ovulation, it was found that the trapped eggs were better preserved than their contemporaries which had entered the uterus at the normal time. Some eggs were still present in the ligated oviducts up to 30 days after ovulation. Recently ovulated one-cell eggs transferred to the uterus of recipients on the 9th day of pseudopregnancy degenerated within 48 hr. It appears that the uterine environment is primarily responsible for the degeneration, particularly of the zona pellucida, rather than straightforward ageing of the egg.

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C. E. ADAMS

Summary.

Female wild rabbits which failed to breed under laboratory conditions were treated with gonadotrophins and artificially inseminated with epididymal spermatozoa. The fertilized eggs so obtained were transferred to synchronous domestic rabbits. Altogether, 185 eggs were transferred to thirty-six recipients. Thirty-three of the recipients maintained pregnancy to term and nearly half of the transferred eggs developed into normal young. Birthweights ranged from 45 to 59 g. Postnatal survival was excellent. Females born in captivity remained sexually immature in spite of attaining normal adult body weights. Sexual development was apparently normal in the males, although most remained shy breeders. Incidental observations on ovarian response, egg size and rate of development are presented.

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C. E. Adams

Summary. In 8 of 12 mink paired for the first time, pairing alone induced ovulation and a short (5 min) interrupted mating led to 8/8 ovulating with normal numbers of corpora lutea. However, in already mated mink, a short mating (Day 7) failed completely or partly (reduced number of ovulations) to induce ovulation. In mink which refused to mate, hCG consistently induced ovulation.

In already mated mink (Day 0) a later mating (Day 7), even if interrupted after 5 min, led to expulsion of the first set of eggs, approximately 50% of which were 'lost' by Day 4 and virtually 100% by Day 6. This effect was not produced by pairing without intromission or by treatment with hCG to induce ovulation. It is concluded that copulation is primarily responsible for the loss of eggs from the uterus, although the exact mechanism remains obscure.

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C. E. Adams

Introduction

Within the past decade the mammalian oviduct and its function has attracted considerable attention, having been the subject of three international symposia (Hafez & Blandau, 1969; Johnson & Foley, 1974; Harper et al., 1976) and several reviews (Blandau, 1969, 1973; Hafez, 1973; Dukelow & Riegle, 1974).

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C. E. ADAMS

Summary.

(1) The amount and distribution of prenatal mortality was estimated in three groups of does: Group 1, a series of 126 first and second pregnancies in seventy-three control does; Group 2, fifteen superovulated and sixteen control does, and Group 3, sixteen does having five ova transferred to one uterine horn and either fifteen or twenty ova transferred to the other uterine horn. (2) Approximately 5 % of the untreated does suffered total loss of their ova before implantation. In does in which implantation occurred, the loss amounted to 9·7% of the ova before implantation and 18% of the embryos after implantation. After implantation the loss was distributed as follows: immediately after implantation, 7·0%; days 8 to 17, 65·%, and days 17 to 23, 27·2%. (3) In superovulated does, having a mean of 28·7 implantations, no reliable estimate can be given for the pre-implantation loss; after implantation 79 % of the embryos were lost compared with 22·6 % in the controls and the mortality tended to occur earlier in the superovulated does. (4) In the Group 3 recipients, there was no significant difference between the two uterine horns in the loss of ova before implantation. After implantation, 23 % of the embryos were lost on the side with few implantations compared with 64 % on the crowded side. (5) It was concluded that `local' factors (deficiency in placental development or inadequacy of vascular supply) were responsible for the abnormally heavy post-implantation loss in uteri with an excessive number of implantations. (6) It was suggested that there exists a `ceiling value' for the number of implantation sites that can be maintained successfully.

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C. E. Adams

Summary. The pattern of egg expulsion/retention was determined in rabbits 24 h after transfer of eggs to the uterus 24–84 h p.c. Nearly all eggs transferred at 24 or 36 h p.c. were expelled into the vagina but from 36 h onwards an increasing proportion was retained in utero, although maximum retention was not recorded until 76–84 h p.c.

In rabbits in which both uterine horns were ligated before egg transfer at 12–48 h p.c., egg development was evaluated 24 or 72 h later, or at term. Practically all eggs transferred at 12 or 24 h perished within 3 days; however, from transfers at 36 h 25% of eggs implanted with 40% survival to term, and further improvement in endometrial receptivity occurred by 48 h. These findings reveal a clear time difference between limitations imposed by endometrial and myometrial function on egg development.

Limited attempts to create more favourable uterine conditions by means of progesterone treatment were unsuccessful.

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C. E. ADAMS

Summary.

When 0·02 ml rabbit semen containing up to 18×106 spermatozoa was deposited into the oviducts of rabbits 0 to 17 hr before ovulation, only 27 to 62% of the expected number of eggs were recovered approximately 24 hr after the ovulating injection (25 i.u. HCG) was given. Recovery was no better at 17 to 18 hr, indicating that the eggs were lost within a few hours of ovulation. Deposition of ram semen and, to a lesser extent, of bull semen was also associated with loss of eggs. Under similar conditions, saline, seminal plasma or dead spermatozoa did not disturb egg recovery. Hence, the loss of eggs was not due to the technique itself disturbing ovum pick-up, except when performed nearer the time of ovulation. Ligating the oviduct near the uterotubal junction did not prevent egg loss.

It was concluded that loss of eggs was caused either directly by capacitated spermatozoa, or indirectly through rupture of the zona pellucida permitting the ooplasm to escape or leucocytes to enter.