News & Advice

Are your cows getting enough zinc to be protected?

Mar 5, 2019 | Dairy, Dairy Animal Health & Welfare, Minerals

Julia Baynes, Veterinarian, Anexa Vets, Morrinsville

As spore counts start to rise across the Central Waikato, it is good to see our farmers getting their zinc supplementation plans underway to protect all classes of stock against facial eczema.

Zinc prevents liver damage by binding with the fungal toxin, sporidesmin, rendering it inactive. It also inhibits absorption of copper in the intestine, which contributes to the formation of free radicals that cause liver damage.

However, there must be adequate levels of zinc in the individual animal in order for it to be protective against facial eczema. 

How do we know whether animals have adequate levels of zinc? 

Accurate dosing is the first step in helping to ensure that your animals have adequate zinc levels on board. However, we need to test the animals to ensure this is the case.
The easiest way to determine whether zinc levels are adequate in your herd is by testing blood zinc levels two weeks after full dosing is underway. The protective range for zinc levels in the blood is above 18umol/L. Anything under that is unlikely to be effective and the herd could suffer liver damage, leading to clinical cases and further problems throughout the year. 

How will blood testing benefit me and my herd? 

We know from previous years that blood zinc levels are highly variable, even when full dosing has been provided, with some herds having up to 80% of their cows with inadequate levels. This is commonly an issue when zinc is provided solely through water treatment, due to individual water intake being highly variable. This variability is affected by rainfall as well as individual cow factors; such as, age, milk production, and pecking order in the herd.
Information gained from zinc blood testing has allowed us to work with farmers to modify the zinc dosing accordingly, to ensure protective levels are met.

An investment in zinc blood testing is money well spent, as it ensures that your zinc supplementation plan is on track, reducing the risk of facial eczema in your herd.

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