Degree Type


Date of Award


Degree Name

Master of Science


Animal Science



First Advisor

James M. Reecy


Infectious Bovine Keratoconjunctivitis is a contagious ocular disease that affects cattle worldwide. It is considered the most significant ocular disease in cattle. The economic impact of the disease has been well documented. The available treatments have yet to show their effectiveness in the prevention and/or control of the disease. The objectives of this study were twofold, to evaluate the effects of IBK incidence and severity on production traits such as weaning weight, yearling weight, and carcass traits and to estimate variance components associated with IBK. Our results support previous findings on the effects of IBK on weaning weight. The results of our study also indicate a decrease in the yearling weight of affected cattle. Furthermore, the decrease in weaning and yearling weights became more pronounced as the severity of infections increased. The heritability estimates obtained from our analyses ranged from .05 to 0.11 +/- .04. Although these estimates are low and similar to other disease and reproductive traits, genetic improvement could be achieved through the implementation of selection programs, designed to increase resistance to IBK.;Most of the research has been focused on the development of treatments for the disease, with debatable success. Additional research is needed on immunological factors present on the ocular surface and their effects in preventing the onset of IBK. In the absence of lysozyme in bovine tears, secretory IgA and lactoferrin are likely candidates implicated in ocular defense against bacterial infections. The first aim of our second investigation was to quantify these two factors in bovine tears with ELISA's. Statistical analyses indicated significant differences between affected and unaffected for SIgA, with lower levels on affected calves. No differences were found in the levels of lactoferrin between unaffected and affected calves. The levels of IgA appear to decrease with increased severity of IBK. The second aim of this study was to estimate genetic parameters of IgA and carry out correlation studies with incidence of IBK. The estimated heritability was moderate, however the correlation between the two traits although moderate was not in the desired direction.



Digital Repository @ Iowa State University,

Copyright Owner

José Eduardo Rodríguez



Proquest ID


File Format


File Size

114 pages