"The apostrophe goes before the s because it is the milk of a cow (i.e., of an animal known as a cow). In other words, it is not about how many cows produced the milk. It is about what kind of animal produced the milk. It is the same with goat's cheese."
Cow's Milk and Goat's Cheese (Apostrophe Placement) www.grammar-monster.com/lessons/cows_milk_goats_cheese_apostrophe.htm
It still needs to be cows irrespective of where the apostrophe goes.
It still needs to be "cows" irrespective of where the apostrophe goes.
Does "A avea" sound like "A bea"? I heard the example fast and made a mistake thinking it was said "A avea lapte de vacă" which led me to think if B sounds differently from V in Romanian or have absolutely the same pronunciation.