Comentário sobre Pará 2:4

עלה עליה זכר פסולה – even though it is not what it prefers, because its costs are expensive and [the owner) loses a lot, and regarding the work it is not what he prefers it does not invalidate it, as it written regarding the heifer whose neck is broken (Deuteronomy 21;3); “a heifer which has never been worked, it is written as עבד – but it is read as עובד. Just as עבד is preferable to him, even עובד is preferable to him, and we derive the sin-offering of the heifer from it. Nevertheless, since that with the rest of the cows it was preferable to him (i.e., the owner), we consider that regarding the sin-offering of the heifer is also preferable to him (i.e., the owner). And further, if you came to validate it, if so, it is also preferable to him (i.e., the owner), and because of this it is invalidated.

Introduction Today's mishnah teaches that if something rests upon the red cow it only disqualifies it from use as a hatat if it is done according to the owners wishes.

העלהו פסולה – Not exactly “brought it up” [upon the cow], but rather, if it went up upon her (i.e. the cow) with the knowledge of the owners, even if it went up on its own, it is invalid. But if it went up [on the cow] without the knowledge of the owners, it is fit/appropriate. But the Halakha is not according to Rabbi Yehuda.

If a bird rested on it, it remains valid. A bird sitting on the red cow does not disqualify it from use as a hatat. This does not count as the bird having performed work for it was not something that the owners wanted to happen.

If a male beast mounted it, it becomes invalid. Rabbi Judah says: if the male was made to mount, it becomes invalid; but if it did so of itself, it remains valid. According to the first opinion, if a male animal mounts the red cow to mate with it the red cow has been invalidated because this is something that the owners would want to happen. And although they would not want it to happen to that particular cow, for this would invalidate it for use as a red cow hatat (worth lots of cash), since they would want it to happen to their other cows, this counts as something that was done with the consent of the owners. Rabbi Judah distinguishes between a case where the owners caused the male to mount the red cow and cases where the bull mounted on its own. For this act to be considered something done according to the owners' wishes, they must take an active part in the act. If they do not, then we cannot consider it an act that disqualifies the red cow.