Funny that you say that, i have also done some experiments with the vegan diet (mostly green leaves, algaes, fruits, and a little nuts, potatoes, cereals, lentils, beans, peas) during a few years and because i have lost muscle mass (not sure if this due to lack of essential amino acids (i make sure to eat plant parts which have all kinds of amino acids but maybe some plant parts are not easily digestable...) or because of parasitic worms, but i plan to eat eggs and maybe some muscles meat this winter. (i will do my best to buy from breeders who respect and take care of animals)
To be safe, you may want to ingest eggs or animals parts which do not have dangerous parasitic worms in their tissues (like taenia cysts).
So maybe chicken or fish or snake/alligator ;) ? https://www.youtube.com/watch?v=ItkFNexQIro
(The problem with fish being the composition of the water... with residues of drugs and toxic substances...)