Date of Award

Spring 2004

Document Type



Life & Environmental Sciences

First Advisor

Jacqueline Brehe

Second Advisor

Marilyn Schendel

Third Advisor

Jeffrey Morris


Although prostaglandin hormone treatments have been used to synchronize estrus in beef cattle to control calving distribution, the question remains whether prostaglandin treatment in combination with natural service will significantly alter calving distribution, and be cost effective for the rancher. In this study, when prostaglandin F (Estrumate and Lutalyse) was utilized, there were no differences between treated and untreated animals in birth weight or mean birth date. However, calving distribution within two twenty-one day periods was significant across treatments. During the first 21 days of the calving season, treated cows calved earlier when compared to the control herd, although the proportion of cows calving during period one was significantly greater for the control group versus the treatment group. During the second 21-day period, 10% more calves were bom in the treatment group versus the control group, however, mean birth date within the second period was not significantly different. These results suggest the prostaglandin F (PGF) treatment altered calving distribution during the first 21 days. Although more calves were bom earlier within the treated group during the first 10 days of the calving season, the observed shifts are not pronounced enough to justify the cost of PGF treatment.