Substitutes for Mammal Meat in people with AGS?

My friend recently got into lm and really locking in the diet. The thing is he has AGS. I've reccomended he eat raw fatty fish and lots of eggs to compensate for the lack of beef. But I don't know if anything wil be as optimal as large mammal meat and milk for our health, also the fish unfortunately is a source of toxins in the quantity he has to consume . If you know anything about the topic or have some sugestions write them down, I think a lots of people could benefit from this information.