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Abstract
Aim: To develop and evaluate a zinc-containing intraruminal controlled-release bolus for protection of calves (175 – 250 kg bodyweight) against facial eczema (FE).
Methods: Boluses releasing zinc, in the form of zinc oxide, at rates ranging from 1.67 to 4.25 g/day were administered to calves which were challenged 4 weeks later with the FE toxin, sporidesmin. The efficacy of the boluses in protecting against sporidesmin-induced cholangiopathy was determined by measuring serum activities of gamma-glutamyltransferase (GGT).
Results: A bolus releasing zinc at approximately 4.25 g/day gave excellent protection against sporidesmin toxicity for periods of up to 5 weeks duration.
Conclusions: This zinc-containing intraruminal controlled-release bolus has the potential to markedly reduce the incidence and severity of FE in calves within a 175 – 250 kg bodyweight range.
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