Testing for Mineral Deficiencies from Hair

Someone mentioned to me the other day they used to have their herd tested for mineral deficiency via tail hair hair samples.

I've tested for DNA verification and polled status, and knew about the milk tests, but didn't realise about the mineral thing.   I thought it was a great idea, especially when following the pat coleby way of life.

I'm wondering if you have done it with your herd of have heard (pardon the pun!) of others doing it?  Where do you get it done?

Square Peg