Mishnayos Shabbos Perek 20 Mishnah 4

גורפין – on the Sabbath, the feeding receptacle/manger that is in front of the ox, we fatten it so that it will not become combined with the sandy matter in the grain that is in the manger in the straw and barley that we place before him and he will cut himself in his food and we remove the straw that is before him to the sides when there is a lot of it so that the animal will not tread on it with his foot and become dirty from the excrement.

וחכמים אוסרים – it refers to both – cleaning out the manger and the straw that is in front of him (i.e., the animal), he should not sweep it to the sides but Rabbi Sosa and the Sages only argued with regard to the real manger (see Talmud Shabbat 140b in Rashi – as opposed to a piece of ground fenced in and used as a manger/אבוס של קרקע ). But a piece of ground that is fenced in and used as a manger, all agree that we do not clean it out, lest one make indentations/holes, , but the Rabbis decreed that a real manger is just like a piece of ground that is fenced in and used as a manger. But the Halakha is according to the Sages.

נוטלים מלפני בהמה זו ונותנין לפני זו – and we don’t say that it does not appear like carrying , because it really appears like it, because an animal is not set aside with food that is taken from its fellow [animal]. And specifically, from before a donkey and we place it (i.e., the food) before a ox, and similarly to it, but not something that is before the ox and placing it before the donkey, for the food of an ox is detestable with the spittle that comes out of its mouth, and the donkey will not eat of it.