J. Anim Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J. Anim Sci. 1974. 38:363-368.
© 1974 American Society of Animal Science
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Warren, J.E.
Right arrow Articles by Williams, W.F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Warren, J.E., Jr.
Right arrow Articles by Williams, W.F.

Interaction of Stage of the Breeding Season and Intrauterine Devices on Estrous Cycle Length in the Ewe1

J.E. Warren, Jr.2, 4,, H.W. Hawk3 and W.F. Williams2

University of Maryland 20740 and U.S. Department of Agriculture 20705

Abstract

An experiment was conducted to determine whether the presence of intrauterine devices would reduce the length of estrous cycles throughout the breeding season. The estrous cycles of ewes with an IUD adjacent to each ovary averaged 9.6 days in length from September through November, and nearly 20 days from December through February. The same ewes showed a similar pattern during a second September to February breeding season.

In the third breeding season, ewes with an IUD in each uterine horn were laparotomized if they had not returned to heat within 9 days after a designated estrous period. Of 54 ewes that were laparotomized during the course of the breeding season, corpora lutea had regressed or were regressing in 49(91%) by day 9, and corpora lutea in the other five ewes had regressed by day 18.

It was concluded that cycles longer than 9 days were usually caused by one or more successive ovulations without estrus, and that the increased mean cycle length for IUD—bearing ewes during the second half of the breeding season was due mostly to a greater frequency of ovulation without estrus.

Footnotes

1 Scientific Article No. A1927 Contribution No. 4849 of the Maryland Agricultural Experiment Station, Department of Dairy Sciences. This work was done at the Agricultural Research Center, Beltsville, Maryland, under a cooperative agreement between the U.S.D.A. and the University of Maryland.

2 Department of Dairy Science, University of Maryland, College Park 20740.

3 Animal Physiology and Genetics Institute, A.R.S., U.S.D.A., Agricultural Research Center, Beltsville, Maryland 20705.

4 Present address: Department of Agriculture, Lincoln University, Jefferson City, Missouri 65101.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1974 by the American Society of Animal Science.