Abstract: An agent for curing states of illness in the digestive apparatus comprising fish fermented by a fermentation process in brine. According to a first method for the production of the agent the fermented fish is encased in capsules that are essentially impermeable to the scent agents that are emitted by the fermented fish. According to a second method for the production of the agent fermented fish in a finely divided form is formed into units, for instance tablets or cookies, and is brought into an essentially solid form. The invention also comprises use of a preparation comprising fermented fish for curing states of illness in the digestive apparatus. Likewise, the invention comprises a method for curing states of illness in the digestive apparatus, wherein a preparation comprising fermented fish is administered to a patient/an animal. Furthermore, the invention comprises an animal feeding stuff comprising fermented fish and methods for the production of such an animal feeding stuff.