Growing Hair without a cooler

[HAB]

I am surprised only one (and that was in passing) has mentioned genetics. Sorry to inform you but if a calf doesn't have "hair genetics" they will not be hairy (why do you think all those baby calves have their hair fluffed when they are 300 pounders?)  Yes, you can make one "hairer" by rinsing, brushing, etc. but you will never get one to grow hair if they do not have the genetic potential.

On the flip side, you can have one with hair genetics and have it not reach the "full genetic" potential of the hair without the hard work!

I agree completely.  Most of out cattle have all kinds of hair, but certain bloodlines in our Galloways slick off in the heat of summer.  Here is a picture of a heifer calf whose hair is all natural, no rinsing, brushing or supplements.  Her legs are slick because they cross belly deep water.  The "pretty" flower is just a nuisance.