Selenium status of cows - deficiency or excess? The development of glutathione peroxidase activity in dairy cows and extensively managed mother cows in Mecklenburg-Vorpommern from 1993 to 1996

摘要

Glutathione peroxidase activity was measured in heparinized whole blood samples from nearly 2000 dairy cows and 350 cows suckling calves between summer 1993 and autumn 1996. Extensively managed cows suckling calves were mostly deficient in seleniumin 1993. There were signs of selenium substitution in some herds from 1994 onwards. The glutathione peroxidase activities of the cows suckling calves were 30% of those of dairy cows and most reflected selenium deficiency. In 1993, glutathione peroxidaseactivities in dairy cows showed adequate selenium substitution. From 1994, rising activity of glutathione peroxidase reflected an increased supply of selenium in dairy herds. The activities of glutathione peroxidase reached a plateau with progressive substitution and therefore could not be used to establish the extent of the selenium excess, but they indicated a tendency towards selenium surplus in dairy cattle feeding without taking into account the real need of the cows.