Published abattoir research found over 40% of cull cows had toxic levels of copper in their livers. Pull back to elevated concentrations and Annie Williams, independent mineral nutrition consultant at Mineral Advice Ltd, suggests more than half of UK dairy cows may be above the threshold — potentially suppressing performance in ways that are almost impossible to distinguish from deficiency. In this conversation, we examine why copper excess is a far more widespread problem than most farmers and advisers currently recognise, and what can realistically be done about it.
The conversation covers the limits of blood testing, why liver biopsy is the only reliable measure of copper status, and how to conduct a proper mineral audit that accounts for every copper input across an animal's lifetime — including concentrates, forages, water, injectables, drenches, and boluses. Annie explains the role of antagonists, why grass-based systems carry higher risk than housed TMR, what palm kernel extract means for formulation, and how copper accumulated in the calf shed follows a heifer right into the milking herd.
The area where knowledge is thinnest — and where Annie expects the most significant development — is the pre-ruminant calf. Adult cattle absorb less than 10% of dietary copper; a pre-ruminant calf bypasses the rumen entirely and absorbs somewhere between 60 and 80%. Current guidance recommends 5 mg/kg dry matter in calf milk replacer, five times what whole milk naturally contains, and nobody is entirely sure where that figure originated. Research underway at Harper Adams, led by PhD student Amy Marsh, is trying to establish what the correct formulation targets should be. If you rear your own calves in the UK or Ireland and are willing to supply survey data and have products sampled, the project would welcome your involvement — find out more at www.mineral-advice.com.
This episode was recorded in June 2026, and all information was correct at the time of recording.
Are you confident your current mineral programme accounts for the full lifetime copper picture — from calf milk replacer through to the milking herd? Share this episode with someone who might find it useful, and if you enjoy ChewintheCud Podcast, please subscribe and leave us a review wherever you listen.
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