Major morphological sperm abnormalities in the bull are related to sperm DNA damage

The influence of sperm morphology and chromatin integrity on bull fertility suggests a strong but undefined biological relationship between these two parameters. In this study we explore this relationship, making use of the Sperm Chromatin Dispersion test, which allows simultaneous observation of sperm abnormalities and DNA fragmentation. Based on spermatozoa from 17 Holstein-Friesian bulls, we determined a relationship between DNA fragmentation and the presence of the “so called” major-type sperm defects. Values for DNA fragmentation index (mean ± SEM) calculated from cells with major-type abnormalities were significantly (P < 0.05) higher (85.05 ± 5.00%) than those from abnormal forms classified as minor-type (17.89 ± 5.55%). Some of the sperm abnormalities, such as double forms, narrow base heads, small heads, shortened tails and proximal cytoplasmic droplets, were only associated with sperm showing fragmented DNA. The simultaneous assessment of sperm morphology and DNA fragmentation has the potential to improve the efficacy of sperm quality assessment in this species.