What’s the selenium status of your herd?

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 first should determine the current selenium status of your cow herd.
Over-supplementing selenium can have a high cost. As well, too much selenium can be toxic to cattle.
The cost of some commercial mineral supplements also can be substantial.
Data suggests about 20 percent of legume and grass-legume forages, and 50 percent of grass and cereal forages, do not provide sufficient selenium for unsupplemented cattle.
The selenium content of forages also will 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 analyzed. Make sure you have a good representative sample.
What if you know the forage in your area is deficient and you already are providing selenium supplements to your herd? How do you know if they are getting enough?
Various studies suggest the selenium requirements of beef cattle can be met by 0.10 mg Se/kg of dry matter intake.
When cattle are being fed during the winter months, the best means of ensuring 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.