Dairy breed bull with complex chromosome translocation: fertility and linkage studies.

A chromosome study was performed on the offspring of an American Brown Swiss bull, which was carrier of a complex chromosome translocation. A total of 10 phenotypically normal calves were examined and a similar complex translocation was detected in five calves. The translocation involved identifiable parts of chromosome number one and eight. Furthermore, the terminal band of chromosome one had been translocated to an unidentified chromosome. One of the calves also carried a 1/29 centric fusion chromosome. Pedigree and chromosome analysis showed that the centric fusion originated from another American Brown Swiss bull. A linkage study was performed and an indication of linkage between the Z blood group system and the complex translocation was found. The fertility of the bull was studied, and it was found to have a severely reduced fertility mainly due to an increased rate of early embryonic mortality.