Photosensitivity An Issue for Some Beef Herds This Summer

Some forages, medications can make cattle more sensitive to sunlight

Published on: Jul 2, 2013

Some common pasture plants and medications are making cattle more sensitive to light this summer, thereby resulting in skin ulcers and tissue death, says Dr. Jeremy Powell, veterinarian for the University of Arkansas ag division.

Photosensitivity, Powell says, is not the same as sunburn. It can originate from otherwise benign crops such as alfalfa or clover. Bermuda grass has also come under suspicion, but it's still uncertain what exactly causes the photosensitivity.

But photosensitivity, which some veterinarians describe as an "allergic reaction to the sun," could be an indicator of something deeper, such as liver damage.

Phil Sims, UA extension staff chair, said he has received calls from beef producers explaining photosensitivity symptoms like skin falling off animals' legs.

Lesions on this cows side indicates photosensitivity. (U of Arkansas photo by Phil Sims)
Lesions on this cow's side indicates photosensitivity. (U of Arkansas photo by Phil Sims)

"Seeing the skin fall off your cattle isn't a common occurrence, and your first thought is 'what are we dealing with?'" Sims says.

Veterinarians said the problem is indicative of liver issues because if the liver is damaged or diseased, its ability to break down plant pigments such as chlorophyll are limited. The pigments build up in the liver and will eventually enter the bloodstream. When they reach the skin, exposure to ultraviolet rays results in skin damage.

Damage to the liver could come from parasites, infections or eating poisonous plants or moldy hay. And coal tar-derived treatments – like tetracycline and some sulfonamides – have been suspected of inducing photosensitivity, too.

Damaged skin on this cows leg is an indication of photosensitivity. (U of Arkansas photo by Phil Sims)
Damaged skin on this cow's leg is an indication of photosensitivity. (U of Arkansas photo by Phil Sims)

Experts recommend that if producers see similar symptoms, they should contact a veterinarian and keep the potentially infected animals in the shade.

The sunburned areas should be treated to halt any potential infections and steroids can help heal the skin.

Source: UA