The gemara explains that the machlokes between R. Meir and Rabbonon about blood letting a sick kodesh animal is whether one is allowed to put a mum in a hekdesh animal that already has a mum. R. Meir darshen from כל מום לא יהיה בו, that it's even forbidden to put a mum in a ba'al mum, whereas the Rabbonon darshen תמים יהיה לרצון that it is only forbidden m'doraysa to put a mum in an animal that is complete. The gemara says that the Rabbonon darshen the pasuk of כל מום to include a case of grama - one cannot put food on the ear of kodesh animal so that it will be bitten off by a predator thereby causing a mum. Although grama is normally permitted, in this case it will be an issur d'oraysa.
The Minchas Chinuch (287) wonders why the Rambam doesn't explicitly write that causing a mum even indirectly would constitute an issur d'oraysa? The Minchas Chinuch suggests that the Rambam holds like R. Meir that placing a mum in a animal that already has a mum is an issur d'oraysa (he understands this from the Rambam in hilchos bechoros 2:13 who says that when one blood lets a sick animal they can't intend to make a mum, implying that if they would definitely be making a mum it would be assur). Yet, the Rambam holds that there is no malkus (as he writes in hilchos issurei mizbeiach 1:8 since it is only learned from a ribuy of כל). Based on the approach that the Rambam paskens like R. Meir, the Minchas Chinuch suggests that the pasuk of כל מום isn't available to teach grama, therefore the Rambam holds that causing a mum is only an issur d'rabonon, not d'oraysa.
The Minchas Chinuch suggests that even according to Tosafos who paskens like the chachamim therefore holding that grama is assur m'doraysa, may still concur that one would not receive malkus because "we never find that one is chayev malkus for a grama". The Minchas Chinuch seems to understand that the issur is violated by the mum being done to the animal, therefore the placing of food on the ear is just "causing" the violation of an issur. However, it is possible that the gezeiras hakasuv of כל מום which teaches that grama is assur, is essentially saying that the issur is not in the result (i.e. the mum), but rather the issur is to do the action that will likely yield the resule (i.e. placing food on the animals ear). If we assume that the issur is violated immediately, just that it is dependent on the mum being done in the end, it would be similar to baking on shabbos where the placing the bread in the oven is an act worthy of malkus (even though it is dependent on the dough getting baked).