Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-28T17:06:53.569Z Has data issue: false hasContentIssue false
  • English
  • Français

Breeding season and ovulation rate in ewes treated with long days in spring followed by a melatonin implant and exposure to a ram

Published online by Cambridge University Press:  02 September 2010

T. Sweeney  and
D. O'Callaghan
T. Sweeney
Affiliation:
Faculty of Veterinary Medicine, University College, Dublin, Ireland
D. O'Callaghan
Affiliation:
Faculty of Veterinary Medicine, University College, Dublin, Ireland
Get access

Abstract

While the onset of the breeding season in ewes can be advanced up to 7 weeks following exposure to long days (44 days) before lambing, a melatonin implant from lambing and exposure to a ram from the summer solstice, this advance is reduced by the absence of a ram. The aim of this experiment was to determine if earlier exposure to the ram and/or exposure to more long days before lambing would further advance the onset of the breeding season. A further aim was to compare the ovulation rate and duration of the breeding season between ewes with a normal and advanced onset of the breeding season due to this treatment regime. Pregnant ewes lambing in mid March were allocated to treatments as follows: (1) controls, maintained on natural photoperiod; (2) 44 LD + mel, exposed to 44 long days (18L: 6D; LD) before lambing followed by a 700-mg melatonin implant after lambing; (3) 90 LD + mel, as in treatment 2, but exposed to 90 LD before lambing; (4) 90 LD + mel + ram, as in treatment 3, including continuous exposure to a vasectomized ram from 10 April. Reproductive state was assessed from serum progesterone concentrations in blood collected at 3- to 4-day intervals from 10 April and ovulation rate was determined during the luteal phase of the first five oestrous cycles in control ewes and ewes exposed to 90 LD + mel + ram. Ewes exposed to 90 LD + mel + ram commenced the breeding season 10 weeks earlier (median date 25 July, range 28 days; P < 0·001) than controls (median date 8 October, range 68 days). Overall, the onset of the breeding season was not advanced in ewes given 44 or 90 LD + mel in the absence of a ram, but a biphasic response was evident, with 40 to 50% of ewes beginning the breeding season at the same time as ewes on 90 LD + mel + ram. Ovulation rate was similar between control ewes and ewes exposed to 90 LD + mel + ram (P > 0·05). The duration of the breeding season was longer in ewes exposed to 90 LD + mel + ram (210 (s.e. 15) days; P < 0·002) than in control ewes (158 (s.e. 10) days), with no difference in date of the end of the breeding season (P > 0·05). Exposure of ewes to 90 LD before lambing in March, followed by a melatonin implant and exposure to the ram from 10 April advanced the onset and extended the duration of the breeding season without an overall effect on ovulation rate. The ram is an important component of this signal sequence.

Keywords

breeding seasonewesmelatoninovulation ratephotoperiodram effect
Type
Research Article
Information
Animal Science , Volume 62 , Issue 3 , June 1996 , pp. 507 - 512
Copyright
Copyright © British Society of Animal Science 1996

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

Barrell, G. K. and Lapwood, K. R. 1979. Effects of pinealectomy on the secretion of luteinizing hormone, testosterone and prolactin in rams exposed to various lighting regimes. Journal of Endocrinology 80:397–405.CrossRefGoogle ScholarPubMed
Bittman, E. L., Dempsey, R. J. and Karsch, F. J. 1983. Pineal melatonin secretion drives the reproductive response to daylength in the ewe. Endocrinology 113:2276–2283.CrossRefGoogle ScholarPubMed
Chemineau, P., Normant, E., Ravault, J. P. and Thimonier, J. 1986. Induction and persistence of pituitary and ovarian activity in the out-of-season lactating dairy goat after a treatment combining a skeleton photoperiod, melatonin and the male effect. Journal of Reproduction and Fertility 78:497–504.CrossRefGoogle ScholarPubMed
Donovan, A., Boland, M. P., Roche, J. F. and O'Callaghan, D. 1994. The effect of supplementary long days, a subcutaneous melatonin implant and exposure to a ram on the onset of the breeding season in ewes. Animal Reproduction Science 34:231–240.CrossRefGoogle Scholar
Donovan, A., O'Callaghan, D., Karsch, F. J., Boland, M. P. and Roche, J. F. 1992. Long days in spring signal the onset of the subsequent breeding season but also maintain current anoestrus in adult ewes. Proceedings of the twelfth international conference in animal reproduction, The Hague. Abstract number 597 (abstr.).Google Scholar
Durotoye, L. A., Rajkumar, R., Argo, C. M., Nowak, R., Webley, G. E., McNeil, M. E., Graham, N. B. and Rodway, R. G. 1991. Effect of constant-release melatonin implants on the onset of oestrous activity and on reproductive performance in the ewe. Animal Production 52:489–497.Google Scholar
English, J., Poulton, A. L., Arendt, J. and Symons, A. M. 1986. A comparison of the efficiency of melatonin treatments in advancing oestrus in ewes. Journal of Reproduction and Fertility 77:321–327.CrossRefGoogle ScholarPubMed
Fraser, S., Cowen, P., Franklin, M., Franey, C. and Arendt, J. 1983. Direct radioimmunoassay for melatonin in plasma. Journal of Clinical Chemistry 29:396–397.CrossRefGoogle ScholarPubMed
Haresign, W. 1992a. The effect of implantation of lowland ewes with melatonin on the time of mating and reproductive performance. Animal Production 54:31–39.Google Scholar
Haresign, W. 1992b. Responses of ewes to melatonin implants: importance of the interval between treatment and ram introduction on the synchrony of mating, and effects on ovulation rate. Animal Production 54:41–45.Google Scholar
Kennaway, D. J., Dunstan, E. A. and Staples, L. D. 1987. Photoperiodic control of the onset of breeding activity and fecundity in ewes. Journal of Reproduction and Fertility 34:187–199.Google ScholarPubMed
Knight, T. W., Peterson, A. J. and Payne, E. 1978. The ovarian and hormonal response of the ewe to stimulation by the ram early in the breeding season. Theriogenology 10:343–353.CrossRefGoogle Scholar
Malpaux, B. and Karsch, F. J. 1990. A role for short days in sustaining seasonal reproductive activity in the ewe. Journal of Reproduction and Fertility 90:555–562.CrossRefGoogle ScholarPubMed
O'Callaghan, D., Donovan, A., Sunderland, S. J., Boland, M. P. and Roche, J. F. 1994. Effect of presence of male and female flockmates on reproductive activity in ewes. Journal of Reproduction and Fertility 100:497–503.CrossRefGoogle ScholarPubMed
O'Callaghan, D., Karsch, F. J., Boland, M. P. and Roche, J. F. 1991. What photoperiodic signal is provided by a continuous-release melatonin implant? Biology of Reproduction 45:927–933.CrossRefGoogle ScholarPubMed
Rekik, M., Bryant, M. J. and Cunningham, F. J. 1991. Effects of treatment with melatonin on the response of seasonally anovular ewes to the introduction of rams. Animal Production 53:203–207.Google Scholar
Robinson, J. J., Wigzell, S., Aitken, R. P., Wallace, J. M., Ireland, S. and Robertson, I. S. 1992. Daily oral administration of melatonin from March onwards advances by 4 months the breeding season of ewes maintained under the ambient photoperiod at 57° N. Animal Reproduction Science 27:141–160.CrossRefGoogle Scholar
Ronayne, E. and Hynes, N. 1990. Measurement of plasma progesterone concentrations by extraction and non-extraction radioimmunoassays. Irish Journal of Agricultural Research 29:109–115.Google Scholar
Ronayne, E., Jordan, B., Quirke, J. F. and Roche, J. F. 1989. The effect of frequency of administration of melatonin on the time of onset of the breeding season in anoestrous ewes. Animal Reproduction Science 18:13–24.CrossRefGoogle Scholar
Staples, L. D., McPhee, S., Kennaway, D. J. and Williams, A. H. 1992. The influence of exogenous melatonin on the seasonal patterns of ovulation and oestrus in sheep. Animal Reproduction Science 30:185–223.CrossRefGoogle Scholar
Sweeney, T., O'Callaghan, D., Karsch, F. J., Boland, M. P. and Roche, J. F. 1992. The importance of the timing of a long day photoperiod signal in synchronising the onset of reproductive activity in ewes. Journal of Reproduction and Fertility, Abstract series no. 9, abstract number 3 (abstr.).Google Scholar
Wayne, N. L., Malpaux, B. and Karsch, F. J. 1990. Photoperiodic requirements for timing onset and duration of the breeding season of the ewe: synchronization of an endogenous rhythm of reproduction. Journal of Comparative Physiology A 166:835–842.CrossRefGoogle ScholarPubMed