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P. T. McGOVERN

Summary.

Five goats were given intravenous injections of sheep spermatozoa at weekly intervals for 21 weeks before insemination with sheep semen. The treatment had no detectable effect on the conception rate. Four of the goats were found to be pregnant when examined at laparotomy or autopsy but there was no evidence of any substantial prolongation of the survival of the hybrid embryos.

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P. T. McGOVERN

Summary.

The survival of goat×sheep hybrid embryos in goats carrying hybrids for the first time was compared to that in goats which had carried hybrids in previous breeding seasons and in goats sensitized against sheep antigens. The findings on the goats carrying hybrids for the first time showed that embryonic death occurred during the 6th week of gestation; twelve live embryos (crown-rump lengths, 22 to 36 mm) were recovered from seven goats examined on Days 35 to 38 of pregnancy, and eight dead embryos (crown-rump lengths, 20 to 38 mm) were recovered from six goats at Days 38 to 43. The size of dead embryos (crown-rump lengths, 7 to 11 mm) recovered from four of five goats carrying hybrids for the second time suggests that survival did not extend much beyond the 3rd week of gestation. Six goats which had received skin grafts and injections of leucocytes from the sheep used for insemination were examined at Days 35 and 36 of pregnancy; live embryos (crown-rump lengths, 25 to 26 mm) were recovered from two goats, and dead embryos (crown-rump lengths, 10 to 16 mm) were recovered from four goats.

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R. B. LAND and P. T. McGOVERN

The experiments described below were undertaken to study the effects of different hormone treatments on follicular development, ovulation and fertilization in lambs. In a similar investigation, Mansour (1959) obtained a low rate of fertilization which he attributed to the use of diluted semen and to the inefficiency of insemination by the vaginal route. In the present experiments fresh undiluted semen was introduced directly into the uterine horns.

Sixteen Scottish Blackface and eight crossbred female lambs were used. The average weight was 16·7 kg (range 11·5 to 26·5 kg). The treatments were begun (Day 0) as soon as possible after the lambs were 50 days of age so that ovulation would be expected to occur when the lambs were approximately 9 weeks old.

The treatments were: (a) Daily administration of 3·0 mg progesterone ('Protormone'; Burroughs Wellcome & Co.) by

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J. L. HANCOCK and P. T. McGOVERN

Summary.

Counts were made of the numbers of spermatozoa in the Fallopian tubes of ewes 24 hr after mating or after insemination with either sheep or goat semen.

Spermatozoa were recovered from all five mated ewes (10/10 tubes), from all eight ewes inseminated with sheep semen (13/15 tubes) and from four of eight ewes inseminated with goat semen (7/16 tubes). The calculated mean numbers of spermatozoa per tube for the three groups were, respectively, 55,332±22,434, 2937±889 and 4640±1958. The low fertilization rate of ewes inseminated with goat semen cannot be explained by failure of the goat spermatozoa to reach the Fallopian tube.

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P. T. McGOVERN, H. Ll. WILLIAMS and J. L. HANCOCK

The object of the experiments described below was to estimate the time at which ovulation occurs in sheep treated with gonadotrophin and to provide, if possible, sheep oocytes of known age in connection with experiments on the hybridization of sheep and goats. Ortavant, Thibault & Wintenberger (1949) found that ovulation occurred about 24 hr after the intravenous injection, given at the beginning of oestrus, of a mixture of pregnant mares' serum (pmsg) and human chorionic gonadotrophin (hcg). Braden, Lamond & Radford (1960) found that ovulation occurred between 20 and 28 hr after injection of hcg in ewes previously treated with progesterone and pmsg. In ewes previously treated with 6-methyl-17-acetoxyprogesterone, ovulation was found to occur 25 hr after injection of hcg (Dziuk, Hinds, Mansfield & Baker, 1964). Moor, Rowson, Hay & Caldwell
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E. M. TUCKER, P. T. McGOVERN and J. L. HANCOCK

Summary.

Experiments are described which were designed to examine the possibility that death of the goat × sheep hybrid foetus is due to the passage of haemolytic antibody from mother to foetus. 'Naturally occurring' haemolytic antibodies to sheep red cells were found in the sera of some goats with normal or hybrid pregnancies. 'Heterologous' anti-bodies, considered to be of the immune type, were found in some but not all goats with hybrid foetuses; these 'heterologous' antibodies were not found in goats carrying goat foetuses. No immune globulins of maternal or foetal origin were found in foetal plasma or in allantoic or amniotic fluids. No real evidence was obtained for the presence of immune globulins on the red cells of hybrids whether or not their mothers had anti-sheep haemolysins in their sera. It is concluded that haemolytic antibodies are not responsible for the death of the goat× sheep hybrid foetus.

The electrophoretic pattern of hybrid haemoglobin was examined.

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P. T. McGovern, C. B. Morcom, W. F. de Sa and W. R. Dukelow

Summary. Treatment of sows with 25 mg progesterone and 12·5 μg oestrone daily between 14 and 23 days of gestation resulted in an increase of 15% of chorionic surface area and an increase in volume of allantoic fluid when examined at 30–35 days of gestation. In contrast, there were no significant differences in chorionic surface area or allantoic fluid volume between treated and control sows examined at 46–50 days of gestation. This suggests that progesterone–oestrone treatment of the sows during early pregnancy has only a short-lived effect on development of the allantochorion.