Effects of different dilution levels on bull- and ejaculate related variability of plasmamembran integrity, acrosomal damage and DNA-integrity of cryopreserved bull spermatozoa

In this study the effects of three different dilution levels (60, 30 and 15 Mio/ml) on quality of cryopreserved bovine sperm were investigated. Particularly it was tested, if effects of dilution in regard to sperm quality were related to the factors bull or ejaculate. The following parameters were analysed in four ejaculates each of 42 bulls: percentage of plasma membrane intact sperm (PMI), percentage of sperm with acrosomal damage (AS) as well as percentage of sperm with a high DNA-fragmentation index (DFI%) following cryopreservation. PMI-values decreased (p < 0,05) with increasing degree of dilution. AS-values were not influenced (p > 0,05) by dilution level. There was a decline in DFI% (p < 0,05) with increasing dilution of the ejaculate. Coefficient of variation for PMI, AS and DFI% were not (p > 0,05) influenced by dilution. The effects of the factor ejaculate on the variabilities of PMI and AS were higher than the effects of the factor bull. Variability of DFI% depended at the highest dilution level more on the factor bull and in the lowest dilution level more on the factor ejaculate. In conclusion, these results show that dilution of sperm has positive as well as negative effects on sperm quality. With increasing dilution the effect of the factor bull on plasma membrane- and acrosomal integrity increased, while it decreased regarding DNA-integrity.