"Duo does not eat chicken."
Translation:Duo ne manĝas kokaĵon.
The root word is 'koko' (chicken/hen). The suffix for foodstuffs is -aĵ-. Therefore, meat of chicken / chicken in the context of being eaten is 'kokaĵo'. Since meat products tend to be uncountable, we don't usually use the plural form. 'Kokaĵojn' would refer to multiple kinds of chicken meat, for example.