Jon, I raise hereford cattle in central Texas and last fall observed a few cows losing hair in patches, specifically in the brisket area, in front of the hind legs and the udder would turn black. Hair would peel off from the tip of the nose toward the eyes. I immediately assumed lice, the most probable and trained thought cause of the problem. My vet called this condition "photosentization", caused by eating alot of green forage in the presence of sunlight. We were beginning to graze winter wheat and the fall temperatures and sunlight were above normal even up to 80 degrees. The symptoms produced no "sores" , just areas where patches of hair fell out, leaving the pink skin. Reminded me of a skin allergy. Occurred in only 2 cows of a group of 30. May not occur in all parts of the country or black cattle.
> I have a small herd of 11 cattle,
> none more than 1 1/2 years old. In
> the last 2 months. 4 of the calves
> (all 6 to 9 months old)have been
> getting raw patchs on their skin.
> The patchs bleed slightly then
> heal, the hair has not grown back.
> I thought they might be rubbing on
> something but that doesnt apear to
> be the case. My neigbor used to
> raise holsteins and thought the
> calves might have lice. The vet
> was out a few weeks ago so I had
> her deworm and delouce them with
> Ivomec+. Its been a month now and
> they are still getting sores. Any
> ideas what this might be and how
> to eliminate it?