Mother Cow produces two things 1) Milk 2) Dung. Milk is outcome of प्राण while dung is outcome of अपान. Immortal matter and mortal matter. Heavenly matter and Earthly matter. Moreover, there is a reference here to the Pravargya.whatever is thrown out as refuse by an organic center of life after assimilation of food is called pravargya. That portion of the food which is retained by the body for sustaining its own metabolism is called Brahmaudan (Food for Brahman’). In each life, the rule of assimilation is assocated with that of elimination.
So when Vedas talk about Cow, Milk and Dung, we should understand them with this concepts in mind. . Prana and Apana, the immortal and mortal, Devas and Bhutas, Life and matter.
In your perceivable reality, living in company of Cow could help you strengthen these realizations very easily with added material benefits (Food, Health, Longevity etc). We exist because of their क्रीडा.