Selenium is an essential nutrient for cattle

By Gary Sliworsky
OMAFRA Rep.

Selenium is an essential nutrient for cattle. Selenium deficiency has been associated with a number of problems in cattle including: white muscle disease, increased susceptibility to infectious disease, reproductive problems, mastitis, and lower than expected rates of gain.

To determine when and how to supplement this important nutrient, however, you should first determine the current selenium status of your cow herd. Over-supplementing selenium can have a high cost. Also, too much selenium can be toxic to cattle. The cost of some commercial mineral supplements can also be substantial.

Data compiled by Alberta Agriculture suggests that about 20% of legume and grass-legume forages and 50% of grass and cereal forages do not provide sufficient selenium for unsupplemented cattle. The selenium content of the local forages will also vary with the soil type. Acidic, poorly aerated soils will tend to produce forages lower in selenium than alkaline and well-aerated soil types.

Average forage concentrations for selenium can indicate if you are in a high area. To determine if your cattle are at risk of selenium deficiency, have your forage analysed. Make sure you have a representative sample.

What if you know the forage in your area is deficient and you are already providing selenium supplements to your herd. How do you know if they are getting enough? The National Research Council (1996) suggests that the selenium requirements of beef cattle can be met by ).1 mg Se/kg of dry matter intake. When cattle are being fed during the winter months, the best means of insuring adequate intake is by force feeding the required amount of selenium mixed in with grain or chopped hay or silage. The optimum amount to add to the ration can be calculated by considering both the content of the mineral mix and the feed analysis of available forages. Remember it is important to consider the balance of all nutrients in the ration.

Next week’s column will continue with more on selenium.