A study published last week in the American Journal of Clinical Nutrition found that dietary protein derived from plant sources built muscle just as well as protein from meat sources. However meat also comes with additional components that are harmful to our health, including antibiotic residue, hormones, saturated fat, trans-fats, endotoxins, cholesterol, Neu5Gc, heterocyclic amines and contaminants such as high levels of metals including copper and arsenic. These undesirable elements increase inflammation and promote various diseases thus making meat a less desirable option when building muscle and long term health are considered.
All the reasons given not to eat carnivores (ie bio accumulation) apply equally well to herbivores.