AMES, Iowa -- Scientists at Iowa State University (ISU) have completed research on pinkeye, a profit-robbing ailment that is common to Iowa’s beef herds, and the findings could mark the beginning of new ways to fight or even prevent the disease.
Jose Rodriguez, a graduate research assistant at ISU, together with Jim Reecy, associate professor of animal science, set out in 2004 to estimate genetic parameters that could aid in the selection of cattle resistant to Infectious Bovine Keratconjuntivitis (IBK), commonly known as pinkeye, and to study immunologic components involved in eye defense mechanisms.
Pinkeye is an eye disease characterized by ulceration of the cornea and inflammation of the conjunctiva. It is a seasonal disease, occurring most often in the summer months. While pinkeye is not life-threatening to cattle, it causes animals to lose weight and therefore results in significant economic losses to the producer. Currently, there is no effective treatment for preventing or controlling outbreaks.
Reecy describes how the research was conducted. “We estimated resistance heritability by using data from the 2003, 2004 and 2005 pinkeye seasons, and we evaluated the effects of pinkeye on weaning weight. In order to evaluate the severity of the disease, a scoring system from 0-4 was developed.”
In addition, tear samples of infected and healthy cattle were collected and evaluated to detect and compare the levels of two proteins, IgA and Lactoferrin, which are known to protect and defend the eye against ocular diseases.
The results showed that the heritability of resistance to pinkeye was estimated to be low to moderate range. “This indicates that slow to moderate progress can be made based on selection of EPDs (expected progeny differences) for pinkeye resistance,” says Rodriguez. Additionally, the effect of infection on weaning weight was rather significant, with infected calves weighing 15.26 kg (33.65 pounds) less than healthy calves.
While the research showed that the levels of Lactoferrin in infected versus healthy eyes did not differ much, levels of IgA were shown to play a significant role in the severity of the pinkeye infection.
“Not only was there a difference in infected versus healthy cattle, we saw a difference in IgA levels when each eye of an infected animal was analyzed separately,” says Rodriguez. Rodriguez’s research indicated that as the amount of IgA in the tears decreased, the severity of the pinkeye infection increased.
“By the time the research is completed, we will be able to estimate EPDs for pinkeye resistance” says Reecy. “This is significant because producers can potentially decrease the expenses associated with treating pinkeye and decreased weight, through selection for healthier calves.”
For more information about the research, visit http://www.ans.iastate.edu/report/air/2006pdf/R2062.pdf.