782. Parameters of Selling Animals

Shabbos 20:4

It is permitted to sell a horse to a non-Jew since a horse is only used to transport people and not to transport cargo. This is not considered an act of labor because of the halachic principle that a living thing carries itself. Just as it is prohibited to sell certain animals to non-Jews, it is likewise prohibited to sell them to Jews whom we suspect may sell them to non-Jews. One may sell a cow to a non-Jew for the purpose of slaughtering it so long as the buyer slaughters it in the seller's presence. One should not sell any animal - not even an ox fattened for slaughter - without making an explicit condition. This is done out of concern that the buyer might delay slaughtering the animal and work it on Shabbos in the interim.

Shabbos 20:5

In a place where the accepted practice is to sell small animals to non-Jews, one may do so. In a place where the accepted practice is not to make such a sale, one may not do so. In all places, however, a large wild animal may not be sold to a non-Jew, just like large domesticated animals may only be sold through a dealer.