Akademik

Не мечи бисер перед свиньями
Avoid doing favo(u)r to people who are incapable of appreciating it or are ungrateful See Не в коня корм (H)
Cf: Don't cast pearls before swine (Am., Br.). Kindness is lost upon an ungrateful man (Am.). То do good to the ungrateful is like throwing water into the see (Am.)

Русско-английский словарь пословиц и поговорок. . 2013.