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 Thompson, D. L. Articles by Nett, T. M. Search for Related Content PubMed PubMed Citation Articles by Thompson, D. L., Jr. Articles by Nett, T. M.

Effect of Reason and Artificial Photoperiod on Levels of Estradiol-17β and Estrone in Blood Serum of Stallions¹

Colorado State University, Fort Collins 80523

Abstract

Five stallions were subjected to a gradually increasing photoperiod beginning on October 15. Maximum daylength (16 hr) occurred on February 8 and was maintained until October 6. Four stallions were kept under the natural photoperiod. Four samples of jugular blood were drawn at 20-min intervals from each stallion once or twice per month from November 6 to November 5. Estradiol-17β (E₂) averaged 79 pg/ml in serum from control stallions and 63 pg/ ml in light-treated stallions (P>.05). Mean E₂ levels in control stallions varied (P<.05) over time and averaged 128 pg/ml during late April as compared to 60 to 90 pg/ml from June through March. Stallions exposed to the artificial photoperiod exhibited no increase in E₂ levels. Estrone (E₁) averaged 132 pg/ml in serum from control stallions and 203 pg/ml in treated stallions (P>.05). Mean levels of E₁ in control stallions varied (P<.05) over time, although no seasonal trend was evident. The pattern of E₁ levels for the treated stallions did not differ (P>.05) from that of control stallions.

¹ Animal Reproduction Laboratory, Department of Physiology and Biophysics.