Epidemiologic Approach to Investigating Abortion Problems in Dairy Herds

Abstract

Abortion problems in dairy herds often pose a frustrating challenge for herd managers and veterinarians trying to solve them. Reasons for this difficulty arise because: 1) there are not well established guidelines on what constitutes an abortion problem, 2) the magnitude of the problem is often difficult to estimate as most abortions are not observed, 3) the inciting event for an abortion may occur months prior to the abortion, 4) known abortificaient agents are identified in only about one fourth of cases submitted to diagnostic laboratories, and 5) given an agent diagnosis, intervention strategies are often limited to herd vaccination or feed changes. As a result of this frustration, an epidemiologic approach to investigating abortion problems was initiated at Washington State University. The investigation protocol consists of seven steps: confirmation of cases, a management questionnaire, development of a farm event listing, collection of bulk tank milk shipment and milk quality reports, construction of temporal plots, a matched case-control analysis, and risk group based sampling. The goal of this protocol is to identify key determinants (risk factors under management control) as potential points of intervention and is intended as a supplemental procedure to standard diagnostic methods.