[teruakohatu]

In New Zealand where cows are all grass fed, they eat 50 kg of grass each day. Milk is concentrated nutrients.

[adrian_b]

Correct.

Moreover, the lactating dairy cows which are kept in industrial conditions usually receive mineral supplements with calcium and/or phosphorus, in variable quantities, depending on the composition of their food, to achieve a maximal milk production, unlike the cows which graze freely.