1. The Gemara quotes two versions of a statement by Rami bar Chama with regard to leading a donkey that is carrying a load on Shabbos.
2. Rebbi Yochanan argues that one who leads a donkey carrying a load on Shabbos is neither Chayav Sekilah nor Chayav Chatas.
3. One may not do an act on Shabbos which causes a vessel to become prohibited from being handled.
4. There is a dispute about whether causing pain to animals is prohibited by the Torah or by the Rabanan.
5. Rabah played with his child on Shabbos by putting him on a donkey on Shabbos.
A BIT MORE
1. Both versions agree that one is Chayav Sekilah if he does so intentionally on Shabbos. The difference in the two versions is whether one is Chayav Chatas if he does so unintentionally.
2. He is not killed if he does so intentionally since one is killed only for a transgression for which one must bring a Korban when done unintentionally. For unintentionally leading a donkey with a load on Shabbos one does not bring a Korban.
3. For example, one may not place an item of Muktzah on a non-Muktzah vessel on Shabbos, because doing so renders the vessel unusable.
4. The Gemara says that Raban Gamliel understood that Tza'ar Ba'alei Chayim is prohibited only mid'Rabanan. Therefore, he did not unload his animal on Shabbos in a way that would cause a non-Muktzah vessel to be unusable until after Shabbos. Since both prohibitions (Tza'ar Ba'alei Chayim, and doing an act on Shabbos which causes a vessel to be unusable) are mid'Rabanan, one does not override the other.
5. When Abaye asked him why this was not prohibited by the decree of the Rabanan against using an animal on Shabbos, Rabah replied that he was not using the animal in the normal manner of usage, since he was putting the child on the side of the donkey. This was not included in the decree of the Rabanan.