Average milk production per cow and year increased the last time on a high level and at the same time the fertility of dairy cows is decreased (BUTLER, 2001). Sperm quality, including sperm morphology, may deteriorate with increasing age of the bull thus becoming a source of concern when using older, progeny-tested AI bull sires. Although a relationship between sperm morphology and fertility after AI in progeny-tested bull sires has been reported, it is yet unclear which sperm abnormalities are most critical. Fertility of A.I. bulls is a very important factor in the reproduction of dairy cattle. Only semen with high quality is requirement for a short breeding interval (days open) and successful pregnancy. Minerals play an important role in both female and male fertility. Calcium for instance is well documented in its role in sperm capacitation (LEHMKUHLER, 2010). Vitamin A for example leads to testicular degeneration in all farm animals. Bulls experience vitamin A deficiency had an fewer total sperm and more abnormal sperm. The aim of the study was to investigate the effect of changing mineral supplementation to sperm quality in A.I. bulls with problems in good sperm quality. 1317874188.php