当牛做马dāng niú zuò mǎ

down-trodden; toil for;work like a beast of burden
❍ 这些过去～的农奴，今天能成为各级领导机关的工作人员，和周总理的亲切关怀是分不开的。(《敬爱的周总理我们永远怀念您》Ⅰ—212)The former down-trodden serfs have now become the staff of the leading organs at various levels. Their progress is inseperable from Premier Zhou’s concern.