by Andrew Cribb (Cribby)

Cribby is the Director/Veterinarian at East Coast Farm Vets

March 2022

With the abundance of feed and great body condition of cows across the district, it’s easy to forget about trace elements, and copper in particular has been on our radar while pregnancy testing cows.

A recent national survey showed that 75% of 1100 pasture samples from around New Zealand did not have adequate copper to meet a cows requirements of 10mg copper per KG of dry matter (less that 1mg of Molybdenum per KG of DM). Requirements for copper will be even greater when soils have higher Molybdenum levels as this mineral interferes with copper metabolism.

Sheep require only half the amount of copper as cattle, which means pastures with 5mg of copper per KG of DM are adequate. Given many farmers in the area treat their ewes with copper pre-lamb, we already know that copper can be very deficient in the region and knowing the levels in all of your stock classes is valuable information.

Copper readily crosses the placenta of pregnant animals where it is required for developing the insulation around nerve fibres of the developing foetus. A deficiency is seen most often as swayback in lambs but will impair the nervous system of all new-borns. This can in turn reduce the "get up and go" of new-born lambs and calves which can be particularly important during inclement weather. The second major function of copper is to provide the scaffolding for bone growth and then the hardening of the bones from cartilage. This is vital for healthy foetal growth, growing a good skeletal frame and preventing broken bones. Copper is also required for a healthy immune system and keeping the whole animal's metabolism functioning to its full potential, which is vital for dams to milk to their full potential and fattening stock to convert food into live weight gain.

With FE spores spiking up prior to the recent rain, many opted to treat with zinc, which will also interfere with copper availability. While there is no dose-dependent response to copper (where more copper equals better performance), there are some well-established levels in the stores that need to be achieved to repair any immediate deficiencies and prevent animals becoming deficient at critical times, especially during pregnancy.

There are a number of ways to supplement stock including injections, which have the benefit of bypassing any Molybdenum in the diet. Intraruminal boluses provide a sustained steady release of copper that is ideal for pregnant dams, but aren't always easy to put into the animal, especially when you have a few hundred to do! Pasture topdressing is a very effective way to quickly raise pasture copper content, but will require some careful grazing management, particularly as pasture levels can be toxic to sheep. Copper can be added to water but again requires the infrastructure of troughs and automatic in-line dispensers.

The key message is to have a full understanding of the "copper budget" of your farm - know where the copper is coming from, what might be impeding its uptake and then ensuring supplements are appropriate for each class of stock at appropriate times.

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