Genetic evaluation of primary cataracts in the German population of single-colored English Cocker Spaniels.

The results of ophthalmological examinations of 615 single-colored English Cocker Spaniels (ECS) were used for prediction of breeding values for primary cataract (CAT) and two different age-related forms of primary cataract, i. e. CAT-early and CAT-late. Breeding values (BV) for CAT, CAT-early and CAT-late were predicted using an animal threshold model and Gibbs sampling. Breeding values were then standardized onto a mean of 100 and a standard deviation of 20. Relative efficiency in reducing prevalence of CAT and CAT-early were compared and we could show that selection based on relative breeding values (RBV) for CAT-early of both parents lets expect the largest relative reduction of prevalence of all forms ofCATs considered here. A selection scheme based on sires or dams with RBV for CAT-early of ≤ 30 would have resulted in a decrease of nearly half of the population mean of 6.67% in the next generation, while a selection scheme based on sires or dams with RBV for CAT of ≤ 90 would have resulted in a decrease of 2.2% or 3.6% of the population mean of 14.96% in the next generation. In contrast to these results, selection for CAT-late is difficult due to insufficient numbers of ophthalmologically examined dogs at higher ages. However, at the present situation the most effective selection strategy to reduce the prevalence of primary cataract in the German population of single-colored ECS would be to consider all animals affected by CAT, because differentiation in RBVs for CAT-early and CAT-late is less efficient due to the unmeaning RBV for CAT-late.