Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Lowell Slyter


The ability to diagnose pregnancy accurately, rapidly and economically before the last six weeks of gestation in the ewe could be of real value as a sheep management tool. An efficient non-surgical pregnancy test could enable the producer to reduce feed costs, increase percent lamb crop and select for fertility. It is important to the health of the ewe and to the survival of the lamb that highly productive animals should be adequately fed. About 75% of the fetus' growth occurs during the last trimester of pregnancy. Therefore undernutrition of the ewe during this part of pregnancy leads to the production of stunted lambs and ketosis in the ewe even though sufficient nutrition might have been present earlier. If sheepmen could determine which ewes were pregnant before any additional feed was needed the dry ewes could be separated from the pregnant ones and either be rebred, fed a maintenance ration or sold. This practice would decrease feed costs while increasing lamb crop percentage. In addition, pregnancy detection would result in the producer recovering a premium price for cull ewes sold in the late fall and early winter when lamb supply is low. As production units become larger and more sophisticated, sheepmen have expressed interest in multiple lambing or "out of season" breeding. Early pregnancy diagnosis could be of special value in the management of such production systems. The ewes diagnosed as pregnant could be removed from breeding and put in lambing quarters while "open" ewes could be returned to breeding pens. This would allow for more efficient use of buildings, labor and equipment. An added bonus is realized when one pregnancy tests ewe lambs and saves only pregnant ones. Several researchers have shown that ewe lambs which conceive or even show heat their first winter are more productive than contemporaries which did not. Thus if pregnancy detection of ewe lambs along with a rigorous culling procedure is practiced a more productive flock will result. The objective of this study was to determine the accuracy of pregnancy diagnosis using various techniques and operators. All techniques were evaluated for safety, ease of usage and time required for diagnosis.

Library of Congress Subject Headings

Sheep breeds -- South Dakota
Pregnancy -- Signs and diagnosis




South Dakota State University