In that way the Rambam is clear. He says in הלכות איסורי מזבח that any object that is נעבד is אסור למזבח. It makes no difference if the object belongs to him or not. But in terms of אסורי הנאה he says in הלכות עבודה זרה פרק ח' הלכה א' that most surprising of laws. He says even on one's own animal, if he is עובד it, it does not become forbidden in הנאה unless he does at least a small מעשה. Clearly he is saying that if he bowed down to his own animal, the animal does not become forbidden in הנאה and it is even מותר באכילה. [It is possible to miss this point of first reading because of the order the Rambam places the subject. At first he says one does not make forbidden in הנאה anything that אין בו תפיסת אדם even an animal unless he does a small act like שוחט סימן אחד. When do we say this. On his own objects. But objects that belong to another, even if he does a complete שחיטה he does not forbid the animal or whatever object it might be. אין אדם אוסר דבר שאינו שלו.
What this means is vast. It means that he is looking at the statement of רב הונא as referring to only his own animal and he is deciding the halacah as Rav Huna. But it also means that he looked at the statement of Rav Amram אין אדם אוסר דבר שאינו שלו and decided the halacah like that also. He decided both statements are true and do not contradict.
Thus he must have had a different version of the statement of Rav Huna.
Rav Huna said in Hulin page מ' ע''ב when a person bows down to the animal of his friend he does not make it forbidden but if he is שוחט סימן אחר he does make it forbidden. The Rambam's version must have said when a person bows down to his own animal he does not make it forbidden בהנאה but if he is cuts one סימן he does make it forbidden.