Franklin Vets Blog
Do your cattle have enough copper reserves for winter & calving?
Copper is an essential mineral for cattle that helps in a variety of animal processes. These are mainly surrounding growth so the risk of copper deficiency is highest in calves, heifers, and late pregnant cows (as the calf takes copper from the cow’s blood to build up its own reserves).
Copper levels and absorption is affected by the season of the year and the ingestion of other metals such as zinc. The optimal time to test liver copper reserves is just before winter. This will confirm that cattle have enough reserves to last them through winter and up to calving. While the emphasis with copper testing is generally around preventing deficiency, in the Waikato we need to also be mindful of toxicity. Too much copper supplementation can make cows very sick and even lead to death.
There are two tests that can be used to determine copper levels-blood tests or liver biopsy tests. Blood tests are easier to perform however to make an informed recommendation liver tests are preferred. This is because the liver is the storage organ for copper and as the blood copper level of an animal reduces, replacement copper will be released from the liver to maintain the blood within the normal range. This can result in normal blood levels while the liver levels are nearly depleted. One way to think about this is like a tank with a pipe at the bottom. The pipe will remain full as long as there is enough reserve but a full pipe doesn’t necessarily predict the level in the tank.
We recommend liver testing a sample of your herd once a year just before winter, especially if you’ve made changes to feeding or fertiliser regimes. Testing a random sample of cows from the herd will provide the best information. Testing cows at the works can be helpful but we are wary of overinterpreting cull cow’s results.