Bovine abortion Part 2: Appraising the laboratory evidence to identify the risks on‐farm

A small hill farm milked 80 Friesian‐cross cows: it reared most of its dairy replacement heifers, but bought‐in a few mature cows from auction each year. All breeding cattle were vaccinated once yearly against bovine viral diarrhoea virus (BVDv), bovine herpesvirus‐1 and Leptospira hardjo. During a six week period at the beginning of 2011, four cows aborted and a full investigation was carried out on the last of these. Radiological examination of the fetal tibia showed the pregnancy had been disrupted first about five weeks before the cow aborted. The fetus died from hypoxia, probably associated with multiple focal myocarditis of either viral or parasitic origin. Results from serological examination of acute and convalescent blood samples obtained from the dam, interpreted within the context of her previous vaccination history, suggested that recrudescence of N. caninum infection together with re‐exposure to BVDv were the main risk factors for abortion occurring in this case.