Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Animal Science


To the cow-calf operator, the single most important factor affecting his economic livelihood is the number of calves produced and weaned for a given year. Unfortunately, due to low reproductive efficiency in comparison with other cattle traits, the possibility of having a calf crop of greater th9n 80 percent at weaning is not too common. The low heritability estimates that have been reported for reproductive performance indicate that little improvement can be expected through selection. To the animal scientist this problem can best be met by the development of a simple and reliable method of inducing for the most part, twins in cows through the use of gonadotropic hormones. The production of a calf crop topping 100 percent and possibly even above 150 percent, similar in comparison to a natural lamb crop·, could be expected. The economic advantages of induced twinning can best be utilized in cows producing calve�� for beef production. From the standpoint of whether or not a beef cow can efficiently suckle twin or triplet calves can probably best be decided by the milk producing abilities of the individual dam. However, it can be assumed ·that crossbreeding and especially the crossing of breeds of beef and dairy together will provide an adequate milk supply. If the contrary is true, rearing the multiple calve artificially as the dairy people have been doing for a number of years would be a possible solution. The purpose of this experiment was to study and compare the ovulatory response between a groups of beef heifers receiving a single gonadotropin injection in the follicular phase of the estrous cycle with a group receiving two injections of the same gonadotropin: one in the luteal phase and the other in the follicular phase.

Library of Congress Subject Headings

Cattle -- Breeding



Number of Pages



South Dakota State University