[Refusal of breeding bulls to eat hay contaminated with horsetail (Equisetum palustre)].

Bulls refused hay from a new batch (coming from a nonintensively fertilized area in Southern Germany). The intake of other components of the ration (silage, concentrates) was not influenced. The visual inspection of the hay revealed a massive contamination (about 12% by mass) by horsetail. According to the reported observations it seems that cattle recognize the plant by its odour, and refuse it if alternative roughage is available, thereby escaping an intoxication.