YOU SAID:

my dad bought half a cow

INTO JAPANESE

私の父は牛を半分買った

BACK INTO ENGLISH

My father bought half a cow.

INTO JAPANESE

父は牛を半分買った。

BACK INTO ENGLISH

My father bought half the cow.

INTO JAPANESE

私の父は牛の半分を買った。

BACK INTO ENGLISH

My father bought half the cow.