The subject of sacrifice quickly leads to heated debate among practitioners of the religio, with each side accusing the other of bad faith. I’m inclined to think that animal sacrifice is a barbaric relic, but others disagree with me.
There is some justification, I think, for looking to Hellenistic practice, as well as Roman and Greek philosophers, for guidance. I’m not saying that these sources are definitive expressions, but that they come out of the same general cultural matrix, and can be legitimately used to understand the direction the religio might have taken if it had not lost the battle with Christianity.
Greek Apollon, it is well known, did not demand animal sacrifice. Indeed, he deplored it. In the Hymn to Apollo, Homer has Apollon demand a sacrifice a sacrifice of barley and meal from his first priests, and he gives clear instructions about how to perform the sacrifice. Apollo is also supposed to have said that the man is more pious who in his heart loves the gods and is temperate and moderate, and who made offerings of burned barley corns at his hearth, over the man who sacrifices and burns a hundred animals at an altar. This, of course, is Apollon. It is not an attitude that can be attributed to the other gods.
Numa, the Roman king who founded the religio is said to have forbidden blood sacrifice. (Cicero, Republica 2.28, Tusuculum 4.3; Livy 1.18. 40.29-14; Dionysius of Halcarnassus 2.59; Plutarch, Numa 18; Ovid, Metamorphoses 15.4.481, Fasti 3.153; Pliny, Natural History 13.87). However, reputable scholars believe that this idea is a much later attribution, related to the mistaken idea that Numa was a Pythagorean. In fact, Numa must have lived before Pythagoras.