Cattle avoid grazing forage near their feces on pasture for more than a month. The relation of cattle feces odor to the rejection was studied in feeding choice tests using cattle. The feeding deterrent of feces odor was investigated using a trough partitioned to allow passage of feces odor through test food to the cattle. The cattle did not feed from the trough containing feces 0-35 days after excretion. Volatile chemicals isolated from feces 0-35 days after excretion by a cold trap method also inhibited cattle from feeding. These results demonstrated that feces odor is a major cause of the unpalatability of forage around cattle feces. The volatile chemicals were separated into ether and aqueous fractions. The ether fraction inhibited the feeding behavior of cattle. Furthermore, the ether fraction was separated into neutral, acidic, and basic fractions. The neutral fraction of the three was bioactive. These results suggested that specific volatile chemicals emitted from cattle feces were deterrents to the feeding behavior of cattle.

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