Masechta Shabbos, Chapter 24, Mishnah 4. This Mishnah too continues to deal with feeding animals on Shabbos.
"Mechatchin es hadelu'in lifnei habeheimah":
One may cut up gourds for an animal so that it can eat them, provided they were picked before Shabbos. And even though gourds are generally fit for human consumption and not for animal feed, one may cut them up and place them before an animal on Shabbos.
"V'es haneveilah lifnei haklavim":
Similarly, one may place a neveilah - an animal that died without shechitah and is not fit to be eaten - before the dogs, and this is so even if it became a neveilah on Shabbos itself. True, on Erev Shabbos it was fit for human consumption and was not designated as animal food, but since it died on Shabbos and became a neveilah, it may be given to the dogs to eat. The view of the Tanna Kamma is that the neveilah is not forbidden on account of muktzeh.
The view of Rabbi Yehudah:
Rabbi Yehudah disagrees and says: "Im lo hayesah neveilah me'erev Shabbos - asurah, lefi she'einah min hamuchan" - that is, if it was not already a neveilah from Erev Shabbos, it is forbidden, because it was not prepared for this purpose while it was still day: before Shabbos it was still fit for human consumption, and only once Shabbos arrived did it become available as animal food, and therefore it is considered muktzeh.
In summary: In this Mishnah we learned that one may cut up gourds that were picked before Shabbos for an animal, even though they are human food, and that one may place a neveilah before the dogs. The Tannaim disagree about an animal that became a neveilah on Shabbos: according to the Tanna Kamma there is no prohibition of muktzeh and it may be given to the dogs, while according to Rabbi Yehudah it is forbidden, since it was not prepared for this before Shabbos.