Morals is not religion. If anything I vehemently dispute religion claiming any ownership of morals. See Plato on morals for more details. But I would say that highest of morals is the highest well-being of humans. This would apply not only from philosophical approach but also from an evolutionary one.
Having said that, I don’t believe eating meat is immoral. It is how we evolved, and eating meat is part of what is to be human.