How frustrating and how far too common it is that after a "full" work-up of a case of bovine abortion one ends up with a final report saying, "Abortion: Cause Undetermined". Unfortunately, we frequently think of abortions as the outcome of in utero microbial infections and that submission of samples to a lab should result in determination of cause. In most labs, testing normally will consist of bacterial, viral or fungal culture, serology and gross and histopathology to scrutinize fetal and maternaltissues for clues of cause for the abortion. Endocrinology, toxicology or genetic testing of submitted samples are rarely done and, too frequently, thorough medical examinations of the dam or herdmates are lacking. Solutions for complex clinical problemsusually involve a "team effort" approach and failures can result anywhere along this chain. In practical terms laboratory testing is not perfect and our ability to clinically investigate many aspects of pregnancy is limited, if not impossible! When reports come back with no cause determined, the question, "what next?" quickly becomes "what are we missing?" Lists of differential diagnoses for non-infectious causes tend to be shorter, less clear-cut, and less often considered than differentials for infectious bovine abortion. We must, however, also include the possibility that some abortions are caused by infectious agents which are missed. This paper addresses non-infectious conditions that potentially could account for some of the missed, or cause-unknown abortions. Six subject areas are discussed. Failure to detect infectious causes. Conditions that disrupt essential supporting endocrine systems. Unrecognized endometrial or cervical diseases. Direct or indirect effects of toxic compounds. Underlying genetic abnormalities. Potential immune-mediated conditions.
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