Karl F. Hoppe

Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Animal Science

First Advisor

A.L. Slyter


The cyclic nature of the reproductive process for females has elicited the focus of reproductive specialists. Alterations in this cycle may lead to a more productive female and consequently a more productive livestock operation. These alterations could entail changing the time of the year conception can occur and the specific times during the week estrus may be displayed. For example, the domestic sheep, Ovis aries, has an estrous cycle length of approximately 17 d, whereas the European beef cow Bos Taurus has an estrous cycle of approximately 21 d. Variations within species lead to ranges for parameters which may place the interval for occurrence of estrus from 14 to 19 d for sheep and 19 to 24 d for cattle. Authors of journal articles and textbooks on endocrinology concede the cyclic nature of the female is a result of the interrelationships of multiple hormones, corresponding endocrine glands target organs and their receptor sites with relation to the hypothalamus and its role in reproduction. The possibility of changing or mimicking the functional properties of the target tissues leads to many hypotheses of how control of estrus can occur. The concept of synchronizing estrus leads to estrous management, causing estrus to occur on a particular day or time in a group of animals. This advantage is of much interest to the producer of livestock. The possibility of using artificial insemination to utilize semen from superior sires is enhanced with estrous synchronization, especially in species such as the sheep which display limited noticeable behavioral changes when estrus occurs. Consequently, the synchronized estrus leads to synchronized parturition. The opportunity to know approximately when an animal or group of animals will be initiating parturition leads to the possibility of uniform age of offspring greater control of nutrition and health during critical periods, improved management by the livestock producer and timeliness of the producer's presence to aid in difficult births and subsequent initiation of suckling, all leading to improved success of the livestock operation through better use of time and facilities. The outcome, of course, is to improve the profit potential of the livestock operation. The experiments contained herein relate to an effort to manipulate the breeding period of domestic sheep specifically to alter the time when estrus will occur. The compound used to obtain this alteration was prostaglandin F2a, a naturally occurring hormone which was produced artificially and donated by The Upjohn Company. Various doses and their effects on breed. Age, fertility, prolificacy, fecundity, synchronization of estrus and subsequent parturition were evaluated and discussed.

Library of Congress Subject Headings

Sheep -- Reproduction



Number of Pages



South Dakota State University


No Copyright - United State