We are beginning siman 3. We learned that there are 5 conditions necessary for an action to be considered tzad deoraysa. In siman 1, we learned the first 3 conditions: that it is b’mino nitzad, it is not already ill or infirm that it could not anyways escape, and it has to be trapped in a way that it is easily accessible. In siman 3, the Chayei Adam discusses the next condition.
The Chayei Adam writes that the animal needs to be an animal which is not b’nei tarbus, an animal which is already domesticated. There are three levels of domestication, fully domesticated, semi-domesticated, and wild. The melacha of tzad applies to animals which are wild, in that on their own they will not come into a person’s domain. An animal which is fully domesticated, such as pet dogs or pet cats, was never going to leave anyways, so the melacha of tzad does not apply to them.
In between, there is a category known as semi-domesticated. For example, animals on a farm do not regularly interact with humans, so they might not be comfortable with humans coming close to them. Nevertheless, even though they go out to pasture during the day, they come back at night. Mideoraysa, the melacha of tzad does not apply to them, but it applies miderabanan.
An animal which was domesticated and then rebels is considered a wild animal and tzad would apply to it. The fact that it began with a different status does not undermine the fact that at the moment, it is not stable and not domesticated.
The Chayei Adam gives examples of geese, ducks, horses, cows or chickens that became wild as examples of animals which are considered wild even if they were previously domesticated. One would be chayav for tzad on Shabbos if they attempted to trap them.
Therefore, the Chayei Adam continues and writes that if one recently purchased a chicken, and it has not yet become fully domesticated such that if given the opportunity, it will run away, retrieving the chicken or preventing the chicken from leaving would be the melacha of tzad. If it ran away from its enclosure, even asking a non-Jew to retrieve it would be assur. It is an issur deoraysa, so even though there is financial loss, the amira l’achum is still assur. (If the issur in question was an issur derabanan, it would be muttar in a case of financial loss, but not in this case, where there is only one shevus.)
Summary
The fourth condition necessary for tzad deoraysa is that the animal is not already domesticated. An animal which is semi-domesticated is assur miderabanan.
