Selenium Dynamics in the Blood of Beef Cows and Calves Fed Diets Supplemented with Organic and Inorganic Selenium Sources and the Effect on their Reproduction

The objective of this study was to compare the effects of feed supplementation with sodium selenite or selenized yeast on serum Se levels and reproduction indicators in cattle. In three beef herds young heifers, cows in late pregnancy, and their calves were randomly grouped by 6. In Herd 1, the mean Se serum levels were 51.01 μg l-1 in heifers, 32.12 μg l-1 in cows in late pregnancy, and 29.07 μg l-1 in their calves. In Herd 2, 27.42 μg l-1 (heifers), Z22.9 μg l-1 (late pregnancy), and 23.46 μg l-1 (calves). In Herd 3, 27.07 μg l-1 (heifers), 22 μg l-1 (late pregnant cows), and 31.05 μg l-1 (calves). Over a 6-month period, the animals in Herd 1 were given selenium yeast supplement; in Herd 2 sodium selenite, whereas Herd 3 served as a negative control. Afterwards, a second blood sample was taken. The mean Se serum levels were as follows: Herd 1 (selenium yeast): 90.73 μg l-1 in late pregnant cows ( p -1 in calves (p -1 (late pregnant cows p -1 (calves p -1 (late pregnant cows), 32.85 μg l-1 (calves). A significant difference was also observed in the second blood sample taken in both the late pregnant cows and the calves between the Herds 1 and 2 (late pregnant cows p p < 0.01). No significant differences were demonstrated between the groups. Herds 1 and 2 showed an improvement in their health status, as compared with the previous period, neither in reproduction indicators nor in the weight gain of the calves