All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Cows are amongst the cattle on which Zakah is due with particular conditions. Some of these are: They shouldn`t be working, they should be grazing from lawful pastures (Public), not fodder-fed. "The second condition for the Zakat on cattle is that they should be grazing since the narration of Anas (As regards the Zakat for the (flock) of sheep) indicated that no Zakah is due on fodder-fed sheep. By analogy, this ruling applies on camels and cows. The same is indicated in the narration of Abu Dawud (For every forty camels, one ‘bintlabun’ (a young female camel which is two years old and already starting the third year), is due as Zakah). Therefore, no Zakah is due on fodder-fed cows, provided that they can`t live throughout a certain period without depending on fodder and so long as they aren`t put up for sale.
If the cows were raised for trade, then the Zakah of trade items is due on them. Al-Imam An-Nawawi said, " If trade items: cattle, fruits or crops reach Nisaab(Minimum amount liable for Zakah), then the Zakah on trade items and that on items themselves shouldn`t be joined; rather, one of them is due."{Al-Majmou`, 6/50}.Since the condition that the cows should be grazing is missing, then no Zakah is due on them as animals. Rather, Zakah becomes due if their owner`s intention-upon buying them- was to put them on sale or made that intention after he had possessed them and he actually started selling them. If this is the case, then he is obliged to give (2.5%) from the value of the cows if it reached the Nisaab of trade items, which is (85) grams of gold.
As for the produced milk, no Zakah is due on it, even if it was put up for sale, because that milk wasn`t owned by virtue of a commutative contract. However, if the money earned from selling the milk reached Nisaab and one whole lunar year passed over possessing it, then the Zakah on money is due on it, and not that due on trade items.
In conclusion, cows fed for a period through which they couldn`t live without depending on fodder, the Zakah on cattle isn`t due on them unless they were put up for sale. If they were, then the Zakah on trade items is due on them. As for the produced milk, no Zakah is due on it. And Allah knows best.