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 Google Scholar Google Scholar Articles by Stellflug, J. N. Articles by Bolt, D. Search for Related Content PubMed PubMed Citation Articles by Stellflug, J. N. Articles by Bolt, D.

Influence of Concentration, Duration and Route of Administration of Melatonin on Reproductive Performance of Spring-Mated Polypay and Polypay-Cross Ewes¹

U.S. Dept. of Agriculture^,5 Dubois, ID 83423

Abstract

The effects of exogenous melatonin on reproductive performance of 737 Polypay and Polypay-cross ewes were evaluated during a late March and April breeding period. Different concentrations (2 or 10 mg) routes of administration (fed vs implanted) and durations of administration (20 or 40 d before breeding) were studied. Estrus was synchronized in all ewes using 60 mg medroxyprogesterone acetate (MAP) in a vaginal pessary. Number of mature ewes lambing/ewe present at lambing was increased (P < .05) nearly 20% by implanting for 40 d with melatonin (75%) or by feeding either 2 (72%) or 10 mg (73%) melatonin for 40 d before spring breeding compared with untreated control ewes (54%) or ewes implanted for only 20 d before breeding (58%). Date of lambing, number of lambs born/ewes lambing and number of lambs born alive/ewe lambing were not altered significantly by treatments. Number of yearling ewes (n = 166 for ewes 1.5 yr old at lambing time) lambing/ewe present at lambing was lower (P < .01; 26%) than that of mature ewes (n = 381, 2.0 yr; 68%). We concluded that feeding 2 or 10 mg melatonin or implanting melatonin for 40 d enhanced reproductive performance and effectively overcame the restrictions of seasonality of breeding in mature ewes. In yearling ewes, 10 mg melatonin increased the number of ewes lambing.

¹ The authors express their appreciation to H. Frederiksen, B. Gardner and D. Willes for technical assistance, to G. V. Richardson for statistical advice and to Vicki Gunter for secretarial help. Gene Link Australia, Inc., New Brunswick, NJ generously supplied melatonin, melatonin implants and assistance in funding temporary labor. Dr. Raiti with National Hormone Pituitary Program, Baltimore, MD supplied the pituitary hormone. Mention of trade names of companies does not constitute an implied warranty by USDA or the authors.

² U.S. Sheep Experiment Station, USDA-ARS, Dubois, ID 83423 in cooperation with Univ. of Idaho, Moscow 83843.

³ Present address: Dept. of Anim. Sci., The Ohio State Univ., Columbus 43210.

⁴ Reproduction Lab, USDA-ARS, Building 200, BARC, Beltsville, MD 20705.

⁵ USDA-ARS.