Association analysis between bilateral convergent strabismus with exophthalmus and milk production traits in dairy cattle

Bilateral convergent strabismus with exophthalmus (BCSE) is characterized i n cattle by a symmetrical antero-medial rotation and protrusion of the eyeb alls. This eye defect is caused by an inherited, centrally insufficient fun ction of the eye muscles recti laterales and retractores. In German Brown c attle a monogenic, autosomal dominant inheritance proved to be most probabl e in complex segregation analysis. In our study running between October 199 3 and May 1995 a total of 200 affected German Brown cows was studied. The i nvestigation of the association between milk production traits and BCSE was based on 10960 German Brown cows. The analysis revealed no significant dif ferences between affected and non-affected cows, nor between cow families w ith and without affected members. There was no indication of an association between milk production traits and occurrence of BCSE within cow families. Linkage or pleiotropy of the BCSE locus with quantitative trait loci for m ilk production traits may be rather unlikely.