Istibra of the Animal
Question :

How many days are required for the Istibra of animals which eat filth (najasah)?

Answer :

The Istibra of the animal that eats human excrement occurs by preventing the animal from consuming human excrement for a specific number of days, in such a way it is considered as not consuming human excrement, and the period depends on the type of animal.
The sharia defines this period for the camel to be forty days; for the cow to be twenty days (and as a recommended precaution it is thirty days); for the sheep to be ten days (and based on a recommended precaution it is fourteen days and as an obligatory precaution this applies to the goat too); for the duck it is five days (and as a recommended precaution it is seven days); and for the chicken it is three days.
For other animals, as an obligatory precaution one should do the Istibra of the animal based on the longest period after which the animal would conventionally not be regarded as one that consumes human excrement, and also considering the size of the animal and comparing it to the mentioned list.