Oestrus suppression and pregnancy prevention in cattle

Summary

Pregnancy control technologies were identified as a high priority for northern Australia to solve the marketing predicament of surplus female cattle faced by northern producers and to optimise pasture availability.

Oestrus suppression and pregnancy prevention were attempted with:
- a bovine intrauterine device
- an ear implant containing a gonadotropin releasing hormone agonist
- three different methods of ovariectomy including ovariectomy with the Willis ovariotome.

The trial was conducted in an extensive beef herd in northern Australia. Good contraception was offered by all methods except the intrauterine device which had many other problems apart from an inability to prevent pregnancy.

There were no significant differences in live weight gain/loss between treatments. Morbidity and mortality were low in all treatments. The Willis dropped-ovary technique was superior to other ovariectomy techniques in its speed and humaneness but suffers from requiring a high degree of skill because it is a blind technique. The agonist implant offers significant potential for non-surgical, reversible suppression of fertility.

Objectives

This project aimed to assess the efficacy of new technologies in suppressing oestrus and preventing pregnancy in commercial, northern, extensive, beef cattle herds.

To establish performance of the technologies, the objectives were to measure fertility, growth, health and welfare of female cattle that had been treated with the new technologies.

Key findings

Effective contraception was offered by all methods except the bovine intra-uterine device (BIUD). Growth differences between treatments were not observed, and in particular, the females treated with the BUID did not grow significantly faster than the controls. Morbidity and mortality were low in all treatments. The Willis dropped-ovary technique was superior to other ovariectomy techniques in its speed and humaneness but requires a high degree of skill. The GnRH agonist bioimplant offers significant potential as a reversal means of pregnancy control in bovine females.

Benefits to industry

Pregnancy control technologies provide means of reducing the surplus of female cattle and controlling mating so that calving occurs when there is optimum pasture availability. This addresses the key issues to calf survival and profitability faced by the northern beef industry.
This project sought to find an acceptable alternative to traditional flank ovariectomy, which is a major and controversial animal welfare issue.

Future research

Since this project, MLA have continued to invest in research in non-surgical options for pregnancy prevention for use in the northern cattle industry.