Cattle and Milk cow

Cattle noun - Domesticated bovine animals as a group regardless of sex or age.

Milk cow and cattle are semantically related. In some cases you can replace phrase "Milk cow" with "Cattle", this terms are similar.

Milk cow noun - Cattle that are reared for their milk.

Cattle and milk cow are semantically related. Sometimes you can use "Cattle" instead a noun phrase "Milk cow".