What is the difference between the animal of a butcher and the animal of a
shepherd?
(a) RASHI and the RAMBAM says that the animals of a butcher are definitely
going to be sold on Yom Tov (or at least he expects them to be), and
therefore, before Yom Tov, he had in mind for the animal to acquire the
Techum of the buyer. (It seems that it works because of Bereirah.) In
contrast, a shepherd does not have buyers from different towns, but only
from his neighbors in his town. Therefore, he has in mind that his animal
should have the Techum of the people of his town, and not his own Techum (if
it differs from the Techum of the town).
The RAMBAN and RAN ask why should Bereirah work in the case of a Shor Shel
Patam? Shmuel holds that Bereirah does not work, even for a Halachah
d'Rabanan like Techumim (37b)!
The BA'AL HA'ME'OR answers that the reason Shmuel holds that Bereirah does
not work in the case of a barrel of wine owned by partners (37b) is because
it is not known for sure that they will divide the barrel on Yom Tov. In the
case of the butcher's ox, the butcher knows for sure that he will sell the
animal on Yom Tov, the only question is to whom he will sell it. Since it is
known that the animal will not have the owner's Techum on Yom Tov, and the
only question is whose Techum it will have, in such a case even Shmuel
agrees that Bereirah works.
The RA'AVAD (Hilchos Yom Tov 5:15) answers that Shmuel holds that Bereirah
does not work only in a case of partners who own something together. Since
they are strict about each other's portion, each wants his own portion to go
with him, to where his Techum is. Therefore, they cannot determine later
which portion each one owned at the onset of Yom Tov. In the case of a
butcher's ox, though, the salesman does not want the ox to have his Techum.
To the contrary, he wants Bereirah to work so that the buyer can take the
animal home.
(b) The RAMBAN and RAN explain that a butcher's ox is like an animal of
Hefker; the butcher removes his own ownership from it as far as the Techum
is concerned. In contrast, the shepherd gives his ox to the townspeople so
that they all have joint ownership of it. As such, it is limited to their
common Techum (and if two people in the town have Techumim in opposite
directions, the ox may not be moved at all on Yom Tov). (The RASHBA suggests
that this rule that the butcher's ox is considered like Hefker might be a
Takanah d'Rabanan for the benefit of the wholesale butcher, so that he will
have buyers and be able to sell his animals.)
Since, l'Halachah, we hold that Bereirah works for Halachos d'Rabanan, in
both cases (Shor Shel Patam and Shor Shel Ro'eh), the animal acquires the
Techum of the buyer, even if he is from a different town.
(c) The BA'AL HA'ME'OR, in the name of Yesh Mefarshim, says that when the
Gemara says that the ox of a butcher acquires the Techum of "every person,"
it does not mean that it acquires the Techum of the person who buys it.
Rather, it means that it is considered to have the Techum of *every* person
who could possibly buy it, and therefore the animal cannot be moved at all
outside of the city.
When the Gemara says that the ox of a shepherd has the Techum of "the
residents of the town," it again means that since there is no Bereirah it
has the Techum of all of the people of the city. Because Bereirah does not
work, according to Shmuel, everyone is a possible owner since it is not
known who will buy the animal. Therefore, it has the Techum of everyone, and
as such it cannot be moved at all if some of the people have Techumim in
opposite directions.
(This question, of whether the ox follows *everyone's* Techum if Bereirah
does not work, depends on a basic understanding of what it means that Ein
Bereirah -- does it mean the Bereirah does not work at all, or that we
cannot determine who the true owner is retroactively, but one of the
possible purchasers was indeed the owner. See Insights to Eruvin 37:1.)