Artificial Insemination and Fetal Programming in Beef Production Systems

Authors

Dempster Christenson, University of Nebraska-LincolnFollow

First Advisor

Rick N. Funston

Date of this Version

5-2024

Document Type

Article

Citation

A thesis presented to the faculty of the Graduate College at teh University of Nebraska in partial fulfillment of requirements for the degree Master of Science

Major: Animal Science

Under the supervision of Rick N. Funston

Lincoln, Nebraska, May 2024

Comments

Copyright 2024, Dempster M. Christenson. Used by permission

Abstract

Pregnancy to artificial insemination and late gestation fetal programming of the next calf crop are central to genetic development, reproductive longevity, calf crop productivity, and efficiency of cow/calf ranching. The purposes of this research are to find methods to improve pregnancy rate to artificial insemination, the growth and reproductive health of pregnant heifers, and the productivity of their offspring. In the first of four studies we found that extending the period of progesterone administration in an estrus synchronization protocol did not significantly hasten estrus response or increase pregnancy rate to artificial insemination, but timing of estrus within the melengestrol acetate artificial insemination protocol demonstrated periodicity of estrus. In the second study we found that supplementation of late gestation heifers with monensin and/or a rumen-undegradable protein did not significantly improve reproductive health of the heifers or affect the productivity of their offspring. Monensin successfully decreased dry matter intake while increasing body weight during treatment and the rumen-undegradable protein successfully increased body weight during treatment. Neither appear to have had a definitive effect in the first two years of the study. In the third study we found that pregnancy to artificial insemination using a one-third sample of semen from three bulls inside a single straw is effective but did not significantly increase pregnancy rate compared to semen from a single bull. Although pregnancy rate by each single bull was very similar, the ratio of paternity within the mixed semen sample numerically disfavored one of the bulls, but Year One results are not significantly different. In a fourth study, that did not have a control treatment and was considered observational, we found that artificial insemination using mixed sex-sorted semen from multiple bulls within a single straw resulted in above average pregnancy rate to artificial insemination for each of three years. When semen quality is reduced by the sex-sorting process, this may be a viable method of artificial insemination and merits further study.

Advisor: Rick N. Funston