rǔ niú / de / sì liào / bì xū / fù hán / dàn bái zhì / cái néng / bǎo zhèng / niú nǎi / de / zhì liàng

乳牛的饲料必须富含蛋白质，才能保证牛奶的质量。

The feed for dairy cows must be rich in protein to ensure the quality of milk.