Been using Tasco brand Kelp for several years on the show calves and with lots of daily management have been able to keep hair on the ones who tend to be good haired. A lot of it is plain genetics we've had herefords and angus calves that barely have any hair in the dead of winter. Are you sure they don't have lice or something similar (are they licking), its that time of year in our neck of the woods. You need to be on a good worming schedule.