HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rawlings, N. C. Articles by Howell, W. E. Search for Related Content PubMed PubMed Citation Articles by Rawlings, N. C. Articles by Howell, W. E.

The Use of Estradiol Benzoate to Manage Lambing Period in Ewes Bred at Synchronized Estrus^1,2,

University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 0W0

Abstract

The induction and management of lambing was studied in a commercial flock of ewes. These ewes were bred at synchronized estrus and managed to lamb three times in 2 yr, with lambings occurring in the sequence of February, September and June. Ewes treated with 2 mg of estradiol benzoate in oil (i.m.) at approximately 17 d prior to term did not lamb in response to treatment. When 2 mg estradiol benzoate was given at 0800 on d 142 of gestation, lambing occurred an average of 37 ± 5 h later in ewes treated in June or September and at 70 ± 10 h later in ewes treated in February. The comparable figures for oil-treated ewes (control) were 70 ± 5 h and 116 ± 9 h, respectively. Altering the time of day of injection or using two injections 24 h apart did not alter the time for injection to lambing. Increasing the dose of estradiol benzoate to 15 mg decreased the time from injection to lambing (43 ± 7 h, ewes treated in February) but also increased the incidence of dystocia (50% incidence). The incidence of dystocia averaged 8% for all other treatments and controls. Death loss of lambs to 1 wk of age was 12% and was not affected by treatment. The length of the lambing period was reduced from 9.0 ± 3.3 d in control ewes to 3.6 ± 1.1 d in induced ewes. A single injection of 2 mg estradiol benzoate given at 0800 on d 142 of gestation or a double treatment, with injections at 2000 on d 142 and 143, resulted in 53% of ewes lambing between 0800 and 1600 on each day of the lambing period, compared with 33% in control ewes.

¹ Supported by a grant from the Saskatchewan Agric. Res. Fund.

² We acknowledge the assistance of I. A. Jeffcoate, Susan Cook, Mariette Hupse, David Currie and the staff at the sheep unit of the Dept. of Anim. and Poultry Sci.

³ Dept. of Vet. Physiol. Sci.

⁴ To whom reprint requests should be addressed.

⁵ Dept. of Anim. and Poultry Sci.

This article has been cited by other articles:

				R. Duggavathi, P.M. Bartlewski, D.M.W. Barrett, E. Bagu, and N.C. Rawlings Short- and Long-Term Effects of Unilateral Ovariectomy in Sheep: Causative Mechanisms Biol Reprod, March 1, 2008; 78(3): 490 - 496. [Abstract] [Full Text] [PDF]