Clinico-pathological findings in cattle exposed to chronic bracken fern toxicity.

AIM: To describe changes in blood and urine analytes in a large group of cattle exposed to chronic bracken fern toxicity, in order to identify parameters of potential diagnostic value.

METHODS

The study was conducted on two livestock farms on which bovine enzootic haematuria (BEH) was known to occur; Farm A grazed a local breed of cows and Farm B grazed Friesians. Group A1 comprised 66 cows from Farm A, Group B 54 cows from Farm B, and Group A2 13 heifers from Farm A. Ten healthy cows were used as controls. A complete physical examination was performed (Group A1), and blood (all groups) and urine (Groups A1 and B) samples were collected. Necropsies and histopathology were undertaken on four cows.

RESULTS

Anaemia, leucopenia, monocytosis, thrombocytopenia, hypergammaglobulinaemia, microhaematuria and proteinuria were detected. Multivariate statistical analyses established three phases of the disease of increasing severity; an initial phase, characterised by an extremely high monocytosis and otherwise normal parameters; an intermediate phase, characterised by monocytosis and moderate changes to other analytes; and a final phase, characterised by normal levels of monocytes and many changes to other analytes.

CONCLUSIONS AND CLINICAL RELEVANCE: Monocytosis, detected in 31% of the younger animals, could represent an initial response to consumption of bracken fern and might be useful as an early haematological marker of BEH.