What do dairy cows eat? Grass.
What does grass eat?
Grass doesn’t eat. It drinks.
What does it drink? It drinks the soil solution, which contains the soluble nutrients the plant requires to grow and maintain health.
It is important to appreciate the root zone of a pasture; what environment are the roots growing in; is it acidic, is it alkaline, are there excessive amounts of some nutrients e.g. sodium, are there deficiencies of some elements, or inefficiencies?. How does the soil hold together when wet; does it become anaerobic?
By looking at the soil below the plants, you can analyse what might be contributing to plant health, which has a direct correlation to the health of the animals that graze on that pasture.
The photo above was taken in a dairy pasture in Victoria.