Hostname: page-component-848d4c4894-v5vhk Total loading time: 0 Render date: 2024-06-23T17:53:28.468Z Has data issue: false hasContentIssue false
  • English
  • Français

Early reproductive failure of ewes in a hot environment V. The conceptus

Published online by Cambridge University Press:  27 March 2009

Margaret Ryle
Margaret Ryle
Affiliation:
Department of Physiology, University of Melbourne
Get access Rights & Permissions [Opens in a new window]

Extract

1. A balanced factorial experiment was carried out with forty-eight Merino ewes. There were two levels of each of the four factors: environmental temperature, thyroxine status, vitamin A intake and progesterone status. Each ewe was killed at 25 days' pregnancy. The embryos and their membranes were weighed and examined histologically.

2. There appeared to be no treatment effects on the embryonic length/weight ratio. The ratio between embryonic weight and ‘conceptus minus fluid’ weight may have been affected. There was no evidence of treatment effects on the degree of differentiation of either the embryo or the chorioallantois.

3. Surviving embryos tended to be large where thyroxine was supplied, i.e. where viability was good, and vice versa. Dead embryos fell into two groups: those less than 3 mm. long and those 6 mm. or more which had probably died shortly before the ewes were killed.

4. There were no significant correlations between the weights of live embryos and mean rectal temperature, plasma vitamin A concentration or any of the histological indices measured in the endometrium. In the hot-room live embryo weight was correlated with the height of the ewe's bladder epithelium (P < 0·01).

5. It is suggested that in the absence of adequate maternal thyroid hormone (i) the trophoblast may enlarge too slowly to stimulate adequately some response in the endometrium essential for maintenance of the embryo, or (ii) disproportionate growth in different parts of the conceptus may result directly in embryonic failure.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 60 , Issue 1 , February 1963 , pp. 105 - 112
Copyright
Copyright © Cambridge University Press 1963

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Bjorkman, N. (1954). Acta anat. (Suppl. 22).Google Scholar
Greenstein, J. S., Murray, R. W. & Foley, R. C. (1958). Anat. Rec. 132, 321.CrossRefGoogle Scholar
Hart, D. S. (1960). N. Z. J. Agric. Res. 3, 565.CrossRefGoogle Scholar
Hawk, H. W., Weltbank, J. N., Kidder, H. E. & Casida, L. E. (1955). J. Dairy Sci. 38, 673.CrossRefGoogle Scholar
Lascelles, A. K. & Setchell, B. P. (1959). Aust. J. biol. Sci. 12, 455.CrossRefGoogle Scholar
Macfarlane, W. V., Pennycuik, P. R. & Thrift, E. (1957). J. Physiol. 135, 451.CrossRefGoogle Scholar
Moore, N. W., Rowson, L. E. A. & Short, R. V. (1960). J. Rep. Fert. 1, 332.CrossRefGoogle Scholar
Nalbandov, A. V., Moore, W. W. & Norton, H. W. (1955). Endocrinology, 56, 225.Google Scholar
Ryle, M. (1961 a). J. Agric. Sci. 57, 1.CrossRefGoogle Scholar
Ryle, M. (1961 b). Aust. J. Sci. 24, 190.Google Scholar
Ryle, M. (1962 a). J. Agric. Sci. 58, 137.Google Scholar
Ryle, M. (1962 b). Aust. J. Sci. 25, 112.Google Scholar
Ryle, M. (1963 a). J. Agric. Sci. 60, 95.CrossRefGoogle Scholar
Ryle, M. (1963 b). J. Agric. Sci. 60, 101.CrossRefGoogle Scholar
Ryle, M. & Morris, L. R. (1961). Aust. J. Exp. Biol. Med. Sci. 39, 79.Google Scholar
Wiltbank, J. N. (1956). J. Dairy Sci. 39, 456.Google Scholar
Wimsatt, W. A. (1950). Amer. J. Anat. 87, 391.CrossRefGoogle Scholar
Wimsatt, W. A. (1951). Amer. J. Anat. 89, 233.CrossRefGoogle Scholar
Yeates, N. T. M. (1958). J. Agric. Sci. 51, 84.Google Scholar