Skip to main content Accessibility help

Photoperiodism in the ewe: 2. The effects of various patterns of decreasing daylength on the onset of oestrus in clun forest ewes

  • M. J. Ducker (a1), C. J. Thwaites (a1) and J. C. Bowman (a1)


In six light-proofed buildings experiments were conducted with Clun Forest ewes to determine whether the date of first oestrus was affected by the absolute size of reduction in the case of an abrupt decrease in daylength and by the rate of reduction in the case of a given total decrease in daylength.

The mean number of days from the onset of the light treatments to first oestrus (the reaction interval) for ewes receiving gradual decreases in daylength of 3·5, 7·2 or 10·9 min/day from 1 July were 66·4, 53·7 or 33·6 days, respectively. The reaction interval for ewes receiving abrupt decreases in daylength of 3·75, 7·75 or 11·75 hr on 1 July were 59·5, 44·8 or 33·6 days, respectively. A control group of ewes at pasture on natural daylength had a mean reaction interval of 66·2 days.

It is concluded that the various light treatments applied significantly affected the date of onset of oestrus in Clun Forest ewes.



Hide All
Clegg, H. T., Cole, H. H. and Ganong, W. F. 1965. The role of light in the regulation of cyclical oestrous activity in sheep. Proc: Conf. oestrous cycle control in domestic animals. Misc. Publs. U.S. Dept. Agric. No. 1005, pp. 96103.
Cole, H. H. and Miller, R. F. 1931. The vaginal smear of the ewe. Proc. Soc. exp. Biol. Med. 28: 841843.
Cole, H. H. and Miller, R. F. 1932. The vaginal smear of the ewe. Anat. Ree. 52, Suppl. p. 50.
Dutt, R. H. and Bush, L. E. 1955. The effect of low environmental temperature on the initiation of the breeding season in sheep. J. Anim. Sci. 14: 885896.
Frazer, A. F. and Laing, A. H. 1966. A preliminary report on the induction of oestrus in sheep with fixed periods of dark-housing. Vet. Ree. 78: 430431.
Grant, R. 1934. Studies on the physiology of reproduction in the ewe. Trans. Roy. Soc. Edinb. 58: 177.
Hafez, E. S. E. 1952. Studies on the breeding season and reproduction of the ewe. J. agric. Sci., Camb. 42: 189265.
Hammond, J. Jr 1954. Light regulation of hormone secretion. Vitamins and hormones. Acad. Press (N. Y.) XII, 157206.
Hart, D. S. 1950. Periodicity in Suffolk sheep. J. agric. Sci., Camb. 40: 143149.
Mauleon, P. and Rougeot, J. 1962. Regulation des saisons sexuelles chez des brebis de races differentes au moyen de divers rythmes lumineux. Annls Biol. anim. Biochim. Biophys. 2: 209222.
Mimura, K. and Asahida, Y. 1959. The environmental factors on the lamb growth, analytically studied with extra-seasonal-lambs. J. Fac. Fish. Anim. Husb. Hiroshima Univ. 2: 365374.
Radford, H. H. and Watson, R. H. 1955. Changes in the vaginal contents of the Merino ewe throughout the year. Aust. J. agric. Res. 6: 431445.
Radford, H. M., Watson, R. H. and Wood, G. F. 1960. A crayon and associated harness for the detection of mating under field conditions. Aust. vet. J. 36: 5766.
Wiggan, L. S. 1967. Studies on fertility in sheep with special reference to artificial insemination and control of ovarian cycles. Ph.D. Thesis, Univ. London.
Williams, H. L. 1967. The intensification of sheep production. Ph.D. Thesis, Univ. London.
Wodzicka-Tomaszewska, M., Hutchinson, J. C. D. and Bennett, N. W. 1967. Control of the annual rhythm of breeding ewes: the effect of an equatorial daylength with reversed thermal seasons. J. agric. Sci., Camb. 68: 6167.
Yeates, N. T. M. 1959. The breeding season of the sheep with particular reference to its modification by artificial means using light. J. agric. Sci., Camb. 39: 142.

Photoperiodism in the ewe: 2. The effects of various patterns of decreasing daylength on the onset of oestrus in clun forest ewes

  • M. J. Ducker (a1), C. J. Thwaites (a1) and J. C. Bowman (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed