beef是可数名词吗?

　　例句：

　　Kenya's beef comes from the zebu cattle.

　　肯尼亚的`牛肉是瘤牛肉。

　　They serve the most delicious roast beef.

　　他们做最美味的烤牛肉。

　　The smell of roast beef permeated the air.

　　烤牛肉的气味弥漫在空气中。