Zinc 

Some farmers have been experiencing problems with facial eczema this summer, even in herds that have a good zinc supplementation programme. This has led to many people supplementing zinc at higher levels and some adding zinc to supplementary feed or using boluses when they traditionally haven’t. There are two potential concerns that you should be aware of if you have made the decision to increase or change your zinc dosing. 

• Zinc toxicity: The levels of zinc recommended for protection from facial eczema are quite close to the toxic level, which means we need to be careful we don’t push cows over the edge. Signs of long term zinc toxicity include cows off milk, milk fever like symptoms, constipation and in severe cases anaemia, jaundice and death. This is more likely when cattle are treated with zinc on a more infrequent basis. 
• As zinc interferes with copper uptake from the gut, supplementing zinc for longer or at higher doses may reduce copper levels more this year than previously. 

Copper 

While zinc supplementation is increased it is important to be aware that this reduces the ability for cows to absorb copper. Low copper can affect production, reproductive performance and growth rates in younger animals.
Liver biopsies are the key to allowing you to make good and economical copper supplementation decisions. Liver biopsies are the only form of testing that can assess copper storage levels and predict if the levels are high enough to get cows through calving and peak production. They will prevent you from wasting money on unnecessary supplementation if your herd already has adequate copper levels, and prevent you from risking copper toxicity by supplementing without knowing the copper status of your herd. a few years ago, we saw at least three herds with copper at toxic levels, because they were feeding PKE and supplementing copper together.

Therefore the important message this year is:

• Don’t risk your animals becoming low in copper and suffering production losses. 
• Don’t waste your money on unnecessary supplementation if you don’t need it. 
• Don’t supplement copper blindly and risk toxicity. 

Contact your local Anexa FVC Vet for advice on trace element testing and supplementation this season. We can also customise a mineral mix for you to meet the exact requirements of your herd, so that you aren’t wasting a cent.