Once a week I give them a portion of raw liver with 100 mcg selenium each.
For 2-3 months I tried to not give them any selenium, but it then seemed as the hair loss worsened after a month or so.
If one give high iodine; selenium is needed too.
I believe the bad press Iodine
have is because the lack of companions like selenium, salt, magnesium etc.
Give the cow a good rock of salt to lick on when she wants.