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J. L. HANCOCK

Summary.

Observations were made on ova recovered from mated, from inseminated and from unmated sows killed at varying intervals up to 144 hr after the onset of heat. The morphological findings on penetrated, pronucleate and cleaved ova are described.

The timing of the events that precede and follow fertilization is examined. The cumulus cell mass (egg-plug) was found around ova only from sows killed less than 8 hr after mating. Spermatozoa were not found in the cumulus until 5½ hr after mating. Penetration and pronucleus formation occurred not earlier than 6 hr after mating. The first cleavage in normal mated pigs occurred 21 hr after mating. Some cleaved ova were recovered earlier than this from sows after 'delayed' mating. The distribution of ova at different stages of cleavage is recorded for sows killed at varying intervals after mating or insemination.

Three of a total of 1677 ova resembled primarily oocytes; all other detectable abnormalities could have arisen in originally normal ova.

The number of spermatozoa on the zona pellucida tended to increase with advancing stages of development, but counts of spermatozoa on ova at the same stage of cleavage recovered at different intervals after mating furnished no evidence that cleavage rate is increased by increasing sperm numbers.

In unfixed ova from unmated sows, spontaneous fragmentation was observed with increasing frequency after 72 hr from the onset of heat; degenerative changes were identified in fixed and stained ova 48 hr after the onset of heat. Cleaved (fragmented) ova from unmated pigs never showed a normal nuclear pattern.

The findings are discussed.

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H. L. BUTTLE and J. L. HANCOCK

Summary.

Sows were injected with hcg 2 days after removal of the litter and were examined at laparotomy for evidence of ovulation at varying intervals from 36 to 44 hr after injection. Ovulation was found to occur about 40 hr after injection. hcg-treated sows shed more eggs than untreated sows. Most treated sows failed to show heat within 6 days of removal of the litter, in contrast with untreated sows.

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H. R. L. BUTTLE and J. L. HANCOCK

Previous experiments (Hancock, 1963) have shown that sheep embryos can survive to the 25th day of gestation following the transfer to recipient ewes of fertilized eggs which have been stored for up to 48 hr at room temperature. This communication records the birth of live lambs at full term following the transfer of eggs after this treatment. The technique used was that described previously. Briefly, eggs at the four-to twelve-cell stage were stored in heat-treated sheep serum, with added streptomycin, in stoppered tubes in the dark and transferred to recipient ewes after storage for 24 or 48 hr. Transfers were made 72 to 96 hr after mating of recipients. The donor Welsh sheep were mated to a Welsh ram; the twenty recipients were mixed Blackface, Soay, Wiltshire, Lincoln and Merino crosses sixteen of which were mated to a fertile
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J. L. HANCOCK and H. L. BUTTLE

Summary.

Untreated sows and sows injected with human chorionic gonadotrophin (hcg) 2 or 3 days after removal of the litter were inseminated into the oviducts. All of eleven untreated sows yielded blastocysts (5·2 blastocysts/sow) at autopsy 7 to 10 days later. Five of twenty-five hcg-treated sows yielded a total of thirteen blastocysts.

The results are described of experiments designed to examine more closely the effects of hcg treatment.

It is shown that the small number of embryos recoverable after tubal insemination of hcg-treated sows cannot be explained by failure of fertilization.

Surgical recovery of eggs was less successful in hcg-treated sows than in untreated sows.

The sites of recovery of eggs were studied in treated and untreated sows examined at autopsy at varying intervals after ovulation. Eggs were found in the oviducts of hcg-treated sows up to 104 hr after ovulation; by this time all eggs had reached the uterus in untreated sows.

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J. L. HANCOCK and G. J. R. HOVELL

Summary.

A technique is described for the surgical recovery of ova from the sow's uterus. With this technique 118 ova were recovered from eight of a total of nine sows operated on 3 to 5 days after the onset of heat. A total of eighty-six ova were transferred to the uteri of six sows of which three farrowed. These three sows had received eighteen, fourteen and ten ova and gave birth to litters of twelve, thirteen and six pigs, respectively. The results are discussed in relation to factors affecting the fertility of inseminated pigs.

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J. L. HANCOCK and G. J. R. HOVELL

Summary.

The results are described of transfers of ova between sheep.

Where necessary, treatment with progesterone was used to synchronize the heats of donor and recipient ewes. pms was used to increase the number of ova shed by donor ewes. Data are given on the onset of heat after treatment in donor and recipient ewes and on the numbers of ova shed, recovered and fertilized among donor ewes.

Of a total of fifty transfers, twenty-six were successful; most of the successful transfers were made to untreated recipients and to treated recipients in which transfer was delayed until the second heat after treatment with progesterone.

Factors that may have affected the success of transfers were: failure to synchronize heats of donors and recipients; the transfer, in progesterone-treated ewes, of ova at the first cycle after treatment; omission of antibiotics from the serum used for recovery, storage in vitro and transfer of ova; the clinical (scrapie) history of the experimental ewes.

There was no evidence of any effect of the time of storage in vitro (up to 5½ hr) on the success of transfers among ova transferred on the day of recovery.

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M. A. BRAY and J. L. HANCOCK

Summary.

The effects of two anti-mitotic agents (colchicine and vinblastine sulphate) on polar-body formation and first cleavage were examined in hamsters treated at varying intervals relative to ovulation. Colchicine failed to suppress either polar-body formation or first cleavage. Vinblastine sulphate suppressed first cleavage but had no effect on polar-body formation.

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J. L. HANCOCK and PATRICIA A. JACOBS

It has been known for many years (Warwick, Berry & Horlacher, 1932, 1933, 1934) that goats readily conceive when inseminated with ram semen but that the hybrid embryos fail to survive beyond the second month of pregnancy. Berry (1938) concluded from an examination of cells from the hybrid amnion that the death of the foetus was unlikely to be due to abnormalities of cell division. The sheep has fifty-four chromosomes comprising six metacentric chromosomes and forty-eight acrocentric chromosomes, while the goat has sixty chromosomes all of which are acrocentric. Berry found the chromosome number of the hybrid to be fifty-seven, but he noted only two metacentric chromosomes.

Berry's illustrations give clear evidence that the techniques available to him yielded preparations greatly inferior to those produced by

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J. L. Hancock and M. G. Daker

Summary. A boar with testicular hypoplasia had 39 chromosomes. Giemsa banded preparations permitted unambiguous identification of an XXY sex chromosome constitution. Spermatogenic tissue was absent as in X chromatin-positive Klinefelter syndrome of man.

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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.