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L. E. A. ROWSON

In the first Hammond Memorial Lecture, presented by Dr McMeeken, he reviewed the rôle of science in animal industry on a global basis and discussed in general terms its application in the future.

In this second lecture, I would like to deal with some of the more specific fields of research in which Sir John was interested and to attempt to project into the future the potentialities of some of the more recent work.

INCREASED PRODUCTION THROUGH ARTIFICIAL INSEMINATION

Throughout his whole life in research, Sir John's primary interest was in methods of increasing production in domestic animals and it is almost certainly true to say that his intense interest in reproduction and growth was secondary to this aim. It is, therefore, quite understandable that, when asked what he considered the most important way in which he had influenced this objective, he replied, 'by the introduction of artificial insemination'.

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J. D. SKINNER and L. E. A. ROWSON

Summary.

The administration of chlormadinone acetate to pubescent lambs suppressed the growth of the reproductive tract as a whole, reduced both ejaculate volume and fructose concentration and delayed the appearance of spermatozoa. Following a period of suppression, a `rebound' effect was seen with fructose levels exceeding those of the controls for a short period and then returning to normal.

Sperm production and motility were reduced and the number of dead and abnormal spermatozoa increased.

Treatment was least effective after the onset of spermatogenesis and the inhibitory effect was counteracted by injection of pituitary gonado-trophin (icsh). There was no effect on growth rate.

Intravenous injection of methallibure appeared to have no effect on testicular growth, and did not delay the first appearance of spermatozoa, but fructose secretion by the seminal vesicles was increased. There was an increase in the number of spermatozoa produced and also in the numbers of dead and abnormal forms. Methallibure did not affect the growth rate.

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J. D. SKINNER and L. E. A. ROWSON

Summary.

Changes during puberty were studied in the live ram lamb by collecting electro-ejaculates and measuring fructose and citric acid concentration and sperm density and morphology. Fructose and citric acid secretion preceded spermatogenesis. Sperm motility improved with decreasing numbers of abnormal spermatozoa. Observations are included on the separation of the penis from the prepuce. In addition, the influence of season of birth on lamb ejaculates was studied. Reproductive development in lambs born in late summer was delayed, androgen secretion being more markedly affected than spermatogenesis. The results of these studies support the view that the onset of male puberty coincides with the time when the testes become androgenically active, the accessory glands begin to secrete fructose and citric acid, and the animal exhibits characteristic male behaviour.

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R. M. MOOR and L. E. A. ROWSON

Summary.

The relationship between the embryo and the corpus luteum was investigated by transferring embryos to various isolated portions of the uteri of 115 non-pregnant recipient ewes allocated to four experiments.

Embryos transferred to sheep with intact uteri (Experiment 1) were shown to be capable of maintaining the corpus luteum irrespective of whether they were transferred to the uterine horn adjacent to the corpus luteum (ipsilateral horn) or to the horn on the opposite side of the corpus luteum (contralateral horn.)

Embryos transferred to sheep with one surgically isolated uterine horn (Experiment 2) maintained luteal function only in the ovary adjacent to the gravid horn. Thus, embryos placed in the isolated ipsilateral uterine horn maintained luteal function in 80% of the recipients, while embryos transferred to the isolated contralateral horn had no effect on the life-span of the corpus luteum. However, if the ipsilateral horn was removed, embryos transferred to the contralateral horn regularly maintained the life-span of the corpus luteum during pregnancy.

Embryos transferred to one isolated horn of recipient ewes that had corpora lutea in both ovaries (Experiment 3) further confirmed the existence of a local unilateral relationship between the embryo and the corpus luteum: since only the corpora lutea adjacent to the gravid horn were maintained.

Embryos transferred to the isolated ovarian half of the ipsilateral horn (Experiment 4) maintained luteal function in 30% of the recipients. Embryos placed in the isolated cervical half of the ipsilateral horn or in the ovarian half of the contralateral horn did not prevent regression of the corpus luteum at the 15th day.

These results are interpreted to signify that the embryo overcomes the lytic effect of the uterus in a local manner. It would appear that the life-span of corpora lutea in sheep with ligated uteri is primarily regulated by the relative position of the lytic non-gravid horn and the corpus luteum, and not by the position of the pregnant horn as such.

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H. R. TERVIT and L. E. A. ROWSON

Early cleavage stage (one-cell to eight-cell sheep ova cultured by Tervit, Whittingham & Rowson (1972) in a synthetic oviduct fluid medium (SOF) with an atmosphere of 5% CO2/5% O2/90% N2 cleaved readily during culture and twelve ova, which had been cultured for 3 to 6 days, developed to viable Day-13 or Day-14 conceptuses in recipient animals. Similar cleavage-stage ova had previously been reported to undergo only limited development during culture (Wintenberger, Dauzier & Thibault, 1953; Hancock, 1963; Kraemer, 1966; Tervit & McDonald, 1969; Moore, 1970; Moor & Cragle, 1971; Moore & Spry, 1972) and to be viable after culture for 1 or 2 days (Hancock, 1963; Tervit & McDonald, 1969; Moore, 1970; Schwartz & Ulberg, 1972; Schwartz, Thompson, Goode & Ulberg, 1972). This communication describes the birth of lambs after the culture of early cleavage-stage ova for up to 6 days.

Welsh Mountain ewes were

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L. E. A. ROWSON and R. M. MOOR

Despite repeated attempts by many workers to transfer eggs to the cow by non-surgical methods, no success was achieved until the recent report of a single pregnancy by Mutter, Graden & Olds (1964). Subsequently, Sugie (1965) using a technique involving the puncture of the anterior wall of the vagina and the inflation of the uterus with carbon dioxide reported two more successful transfers; one of which however was followed by abortion.

The difficulty inherent in the technique of non-surgical transfer of cow eggs was attributed by Rowson, Lamming & Fry (1953), Harper, Bennett & Rowson (1961) and Bennett & Rowson (1961) to at least two causes (i) uterine infection, and (ii) expulsion of the eggs via the cervix, the two factors acting either singly or in conjunction with each other. Our efforts to overcome these

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R. M. MOOR and L. E. A. ROWSON

Summary.

The ovary not containing the corpus luteum was removed from each of fifty-two ewes on Day 8 of the cycle. These animals were then allocated to one of the following groups. Group 1 : (control) received no further treatment. Group 2: the contralateral uterine horn, i.e. located on the side opposite to the corpus luteum, was removed. Group 3 : the ipsilateral uterine horn, i.e. located on the same side as the corpus luteum, was removed.

Neither unilateral ovariectomy alone (Group 1) nor the removal of the contralateral horn (Group 2) affected the length of the post-operative oestrous cycles. In contrast, extirpation of the ipsilateral uterine horn (Group 3) resulted in a significant extension of the oestrous cycle and thus of the life-span of the corpus luteum. The results suggest that the ovaries of the cyclical sheep are probably affected by the uterus in a local manner.

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J. P. BENNETT and L. E. A. ROWSON

Summary.

A technique of cannulation of the epididymis of the bull with the subsequent establishment of a patent fistula is described, which allows for the repeated collection of epididymal spermatozoa and secretions from the living animal.

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R. NEWCOMB and L. E. A. ROWSON

A.R.C. Unit of Reproductive Physiology and Biochemistry, Cambridge

(Received 12th November 1974)

In sheep, the transfer of two- to four-cell eggs from the oviduct of donors to the uterus of recipients results in a poor conception rate, while uterine transfers of Day-3 (eight-cell) eggs (Day 0 = day of oestrus) give a satisfactory conception rate (Averill & Rowson, 1958). Moore & Shelton (1964) found that transfers to the oviduct were more successful than those to the uterus, but Trounson & Moore (1974) found that the site of transfer of Day-3 eggs had no effect upon their subsequent survival. In sheep, most eggs are present in the uterus 66 hr after ovulation (Holst, 1974), whereas in the cow, which ovulates about 12 hr after the end of standing oestrus, Hamilton & Laing (1946) could find no eggs in the uterus before 96 hr after the end of oestrus. Thus, although the

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L. E. A. ROWSON and R. M. MOOR

Summary.

Morulae and blastocysts obtained from ewes 5, 7 and 9 days after oestrus were transferred to 120 recipients whose oestrous cycles were either synchronized or ± 2 or 3 days out of phase relative to the onset of oestrus in the donors.

When synchronization was exact 75% of all recipients became pregnant. A high proportion of pregnancies were, in general, also obtained where the onset of oestrus in the recipient differed from that of the donor by ±2 days. With a difference of ±3 days, however, only 8 % of ewes became pregnant. The survival of 5-day morulae transferred to 7-day recipients was lower than when 9-day blastocysts were transferred to 11-day recipients.

The results are discussed with reference to possible factors associated with early embryonic mortality.