|"We're still looking for the magic bullet to prevent pinkeye. We've had it in hot and cool weather, in calves from first-calf heifers and cows. We have no way to predict it,” says Dennis Maxwell, beef research supervisor at Iowa State University's McNay Research Farm.
You're checking the cowherd on a hot summer day when you spot a calf with a weeping eye. Is it just a weed seed or is it the start of pinkeye? What should you do? Pinkeye, or infectious bovine keratoconjunctivitis (IBK), is a contagious bacterial disease that affects the eyes of beef cattle. Estimated to cost the cattle industry $150 million annually, pinkeye causes tearing, inflammation and ulceration of the cornea. Permanent blindness can occur in severe cases.
The bacterium Moraxella bovis is a known cause of pinkeye. Researchers recently found a second bacterium, M. bovoculi, as a potential carrier. Environmental factors such as warm weather, ultraviolet light from the sun, fly populations, dust and tall pasture grasses and seed heads also contribute to cornea damage.
If you suspect pinkeye, frequently observe the herd to see if other cows or calves develop weeping eyes. Once you observe whitening of the cornea in an animal, work fast to reduce the spread of pinkeye, says Annette O'Connor, epidemiologist at Iowa State University (ISU) College of Veterinary Medicine.
The best methods to prevent pinkeye are fly control, grass and weed control, the use of vaccines prior to an outbreak and antibiotic use on affected animals.
"It's difficult to know what is the best method for preventing pinkeye, so control the things you can, such as fly control or clipping pastures,” O'Connor says.
She and other ISU faculty conduct pinkeye research at the McNay Research Farm in south central Iowa. Dennis Maxwell, beef research supervisor at McNay, oversees research efforts on the 400-head purebred Angus cowherd. "We've had a perennial problem with pinkeye and have tried everything from fly tags and feeding antibiotics to eye patches and vaccines. So far, we haven't found the miracle to control it,” he says.
The research farm was part of an 1,878-head study of pinkeye in Black Angus cattle from 2003 to 2005. Four other cowherds in Indiana, Wisconsin and Iowa were included in the study, conducted by ISU graduate student Jose Rodriguez with help from animal
scientists Abebe Hassen, J. R. Tait and James Reecy.
During the study, incidence of IBK ranged from 30% to 52% in the ISU herd. No vaccinations were given prior to turnout and pinkeye treatment was limited during the grazing season.
Calves were scored for evidence of pinkeye as they were weighed at weaning. Pinkeye-affected calves showed a 26-lb. reduction in weaning weights. Calves with one eye infected averaged 19 lb. less than unaffected calves, while calves with pinkeye in both eyes weighed 40 lb. less than unaffected calves, says Tait, ISU associate scientist in animal breeding and genetics.
Preweaning incidence of pinkeye also impacted yearling weight performance, Tait says. "Only a subset of the animals was followed through harvest, but there was a trend for reduced hot carcass weight for pinkeye-affected calves. The trend appears to be that they are affected for life.” BT