Line 3: "You don't stop laughing because you grow old. You grow old because you stop laughing." -- Michael Pritchard
Jung says (Wilhelm-Baines, p.119) that in the Parsee religion fire and care of the cow are connected. The Divine Light, or fire, was manifested in the mineral, vegetable and animal world before it appeared in human form. Its animal incarnation was the cow, and Ahura-Mazda was nourished on her milk.
My view is that hex.30 is about manifestation, the things that are or become visible. In the world, but also in your mind: consciousness, acquire awareness, brightness: the capacity to separate things. (Hex.29 as its counterpart not 'invisibility' but the manifestation of the other half (right half) of the brain. Coping with feelings, fears, desperation).
I think for a farmer a herd of cows is the most manifested way of being a farmer. All this sun turned into big animals. A crop is a nice thing too, but it disappears every year, sold or eaten. The herd of cattle stays year after year.