Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Animal Science

First Advisor

Lowell Slyter


Heifers gain at a slower rate, generally require more feed per unit gain and sell at a lower market price than steers. Due to the fact that heifer carcasses are commonly fatter and contain more waste trim than steers, the value of a heifer carcass is routinely less than that of a steer carcass of comparable yield and quality grade. In the past, the ways in which the livestock operator could increase his profit from feeding heifers were limited. Differential cost of feeder heifers versus steers and feed cost were the major criteria involved in his decision of whether or not to feed heifers. Hormone implants are effective in improving gain and feed efficiency with both sexes. Even with the added benefits of implants, however, heifers have not reached or maintained the level of productivity that steers have. The Hei-Gro device is marketed as a nondrug growth stimulant for heifers and was made available to cattle feeders in 1976. While its mode of action is not specifically known, it is reported to in increase feed efficiency and average daily gain in feedlot and pasture heifers. A primary objective of the research reported was to determine if any additional value could be obtained by using the Hei-Gro device in combination with Synovex-H implants. Of additional interest was whether or not separation of steers from heifers in the feedlot would cause increased performance. Another objective was to determine how treatment with the Hei-Gro device would affect the reproductive tract and estrous activity of the heifers.

Library of Congress Subject Headings

Heifers Growth factors



Number of Pages



South Dakota State University