Controlling What We Can Control

Limiting Embryonic/ Fetal Losses

Abstract

While there is sometimes a feeling of hopelessness when we are asked to solve a herd problem involving "occult" loss of pregnancies, there are a few things we as veterinarians can do to reduce the risk of embryonic and fetal losses. For many infectious causes of pregnancy attrition, there are vaccines of various safety and efficacy. Some of them are effective because elegant research on host-pathogen interactions has pointed the way to exquisitely specific and effective antigens and adjuvants; some are effective in spite of a lack of such information; and a few are not particularly effective. But not all pregnancy losses are the direct result of fetal infections. This paper will attempt to address the increasingly long list of causes of pregnancy disruption in cattle, and to point out some preventive measures reported to be effective, or in the case of some as yet unproven interventions, at least make pathophysiologic sense. Topics will include measures to diminish the impact of non-infectious causes of pregnancy disruption (trauma, heat stress, twinning, plant and other ingested toxins); a few infectious causes where preventive intervention is likely to pay off (e.g. infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD) venereal campylobacteriosis, leptospirosis); some "iffy"areas where the payoff is not as certain; and a discussion of the expectations of a vaccine against any reproductive pathogen. A brief mention will be made of some current thinking on efforts to reduce early pregnancy loss through nutritional management of dairy cows.