Can cattle be selected to reduce pinkeye incidence?
Pinkeye has long been a costly nuisance to cattle producers. Eye infections sometimes lead to partial or complete blindness in one or both eyes. Reduced beef production in the form of lowered weight gain, milk production, body condition, and, eventually, even poorer reproduction can result from eye infections and lesions.
One of the culprits that initiates and spreads eye problems between herds and among herdmates is "pinkeye," or more properly called Infectious Bovine Keratoconjnctivits (IBK). An excellent Oklahoma State University fact sheet about the prevention and treatment of "pinkeye" is available online at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2689/VTMD-9128web.pdf.
Iowa State University (ISU) animal scientists analyzed field data from ISU herds and cooperator herds in 2003 and 2004. They sought to estimate the genetic measurements that could aid in the selection of cattle resistant to IBK. They found a decrease in weaning weight of 20.9 pounds per calf infected with pinkeye.
The analysis of the field data revealed an estimate of 0.18 for heritability of resistance to pinkeye. This estimate is considered to be of low to moderate heritability, which indicates that slow to moderate progress can be made based on selection for IBK resistance. It does mean that, over time, if we select replacements from cows that are not prone to having eye problems (especially pinkeye), we should be able to gradually reduce the incidence of pinkeye in our herds.
They also studied the immune components involved in eye disease defense mechanisms. Tear samples were collected from the eyes of 90 calves in 2004 in order to quantify immunoglobulins (commonly called antibodies).
The result of this analysis indicated that as the amount of Immunglobulin A in the tears increases, the likelihood of infection and/or the severity of infection decreased. This information would suggest that properly fed, properly immunized cattle, with a strong immune system will be more resistant to pinkeye. — Glenn Selk, Oklahoma State University Cattle Reproduction Specialist