Selenium status of cows effects their calves

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Science summary

In many areas of the world, feed grains and forage crops contain inadequate concentrations of selenium. Livestock require selenium as a cofactor for the antioxidant enzyme glutathione peroxidase. Supplementation of feeds with selenium has greatly reduced the incidence of deficiencies. However, in certain situations, sodium selenite, the most common form of selenium used in animal feed, may be ineffective in preventing selenium deficiencies.

Dr. Bo Pehrson, of the Swedish University of Agriculture Sciences, says that inorganic selenium, such as sodium selenite, are not readily transferred to the milk. Therefore, calves nursing cows fed rations supplemented with sodium selenite may develop marginal selenium deficiencies. The problem is that rumen microbes convert the selenite to a less bioavailable form. Dr. Pehrson recommends replacing the sodium selenite in cattle rations with organic selenium (Sel-Plex). Sel-Plex contains selenomethionine and other naturally-occurring organic selenium compounds, which are not affected by rumen microbes. As a result, more of the supplemented selenium is absorbed and transferred to the tissues.

To compare the effect of the two forms of selenium on cows and their calves, Dr. Pehrson conducted a study involving 103 cows. The cows were fed a supplement that contained 30 ppm selenium in either an inorganic (sodium selenite) or an organic (Sel-Plex) form. The base ration was selenium-deficient. Blood samples were collected from the cows and their calves for selenium assay. The calves were approximately 22 days of age at the time of sampling. Milk samples were also obtained. The assay results are summarized in Table 1.

Table 1. Comparison of inorganic (sodium selenite) and organic (Sel-Plex) on cows and calves.

1GSH-Px=Erythrocyte glutathione peroxidase activity.

There was no difference in supplement consumption between the two groups. However, the form of selenium influenced the selenium status of the cows and calves. Cows fed Sel-Plex had higher concentrations of selenium in their blood, serum, and milk. Also, these cows had higher glutathione peroxidase activity in their erythrocytes.

The form of selenium fed to the cows impacted the selenium status of the calves. Selenium concentrations in the blood and plasma as well as the glutathione peroxidase activity were higher in the calves from Sel-Plex-fed cows than they were in calves from cows fed sodium selenite. According to Dr. Pehrson, whole blood selenium concentrations below 100 ug per liter are indicative of a selenium deficiency. Under this criteria, calves from cows fed the inorganic selenium were deficient.


Dr. Pehrson reported the following correlations between the measured variables:

According to Dr. Pehrson's study, organic selenium improves the selenium status of cows and calves better than inorganic selenium. He added that his results are in disagreement with a previous study conducted in another laboratory. However, in the previous study, he pointed out, the selenium content of the base ration was nearly 10-times higher.