Purpose: It has been repeatedly speculated that a deficiency in copper (Cu) or an excessive provision with dietary manganese (Mn) could play a role in spongiform encephalopathies [bovine (BSE) and others]. Therefore, commercial cattle feeds were screened for their content of these minerals.
Design: The historical development of the levels of Cu and Mn in Bavarian cattle feeds was evaluated and the levels compared with feeding recommendations.
Materials and methods: We report declared Cu and Mn contents from proprietary cattle feeds sold in Bavaria between 1978 and 1998.
Results: Mn contents in ruminant feeds were generally high, and there was a trend of increasing Mn levels in ruminant feeds between 1980 and 1990, which was in synchrony with an increase in internationally recommended Mn levels for ruminants. Recently, the recommendations have been modified again to lower levels.
Conclusion: Although no causative connection to the occurrence of BSE can be made, the practice of high Mn supplementation of proprietary cattle feeds should generally be reassessed.