Making the Most Out of your Culled Cows
May 2023

With winter coming up, it is it is important that we provide our animals with the right amount of trace elements necessary to get them through the deficient periods. Trace elements, particularly copper and selenium, play an essential role in production and the immune system of cattle. Knowing your herds status will allow you to effectively supplement when they need it the most.

Copper has a key role in the immune system, musculoskeletal development, and in milk production. It is stored in the liver and slowly released into the bloodstream to maintain adequate levels. The best way to assess copper levels is to check how much is stored in the liver.  

Deficiency commonly occurs when there are high levels of certain other elements in the grass, such as molybdenum (Mo), which significantly increases as we go from summer through to winter and can cause large reductions in the availability of copper from the diet. Copper demands are also significantly increased in late gestation. On the other hand, some feeds, especially palm kernel, are high in copper so we can run into issues with copper toxicity if supplementing and not monitoring intakes correctly.

Zinc counteracts absorption of copper so as we come out of the facial eczema season it is a good time to check your cows have sufficient levels. Some of the signs you may see with deficiency include poor production, ill thrift, pale mucus membranes, sudden death, and diarrhoea.  

Selenium is required for normal growth, fertility, and aiding the body’s immune response to disease and inflammation. Maintaining adequate levels can help reduce incidence of diseases such as retained foetal membranes and mastitis. Selenium deficiency is more likely to occur in spring when pasture growth rates are rapid, and rainfall is higher. Some of the clinical signs of deficiency include ill-thrift, poor growth rates in young cattle, and infertility. The selenium concentrations in plants are often insufficient to meet the requirements of grazing ruminants so it is a good idea to keep an eye on it.

The best way to ensure your cows have adequate levels of these elements is through liver biopsies. This can be done in a live animal or through the works when you send some cows off. Culled cows from the breeding herd in late autumn or early winter can provide valuable information on your animal’s copper storage levels before the increased demands of late pregnancy and lactation. Unfortunately, blood testing cannot accurately predict the amount of copper storage in the liver but it can be used to determine selenium levels.

Autumn is a great time of the year to monitor these trace elements so contact your vet to discuss testing methods as well as appropriate supplementation if necessary.