There are no nutrients in animal corpses that we need that cannot be obtained from other sources. In 100% of cases that I have experienced where people were convinced that they needed to eat 'meat', after only brief conversation it was clear that the individuals had not done proper research into the topic.

As far as Omega 3s go - there are numerous vegan ways to obtain them and counteract the problems caused by excessive Omega 6s. Ground linseeds/flax seed is one such approach. I buy a bag of ground flaxseed mixed with ground nuts and drop some on my cereal each day.. That's all that's needed.