beef是可數名詞嗎?

例句：

Kenya's beef comes from the zebu cattle.

肯尼亞的`牛肉是瘤牛肉。

They serve the most delicious roast beef.

他們做最美味的烤牛肉。

The smell of roast beef permeated the air.

烤牛肉的氣味瀰漫在空氣中。