Relationship between quality parameters and fertilizing ability of cryopreserved sexed bull sperm

The aim of the experiment was to assess the correlation between sperm quality parameters and field fertility after AI with sex-sorted (X-bearing) bull semen. A total of 32 ejaculates from 26 Holstein-Friesian bulls were analyzed to assess sperm motility parameters (CASA), viability (SYBR-14/PI), apoptotic-like changes (YO-PRO-1/PI), chromatin structure (SCSA), and ATP content. In order to determine sperm fertilizing ability, 816 heifers and 727 cows were inseminated. Ultrasound diagnosis of pregnancy was performed on day 35 after insemination. For each ejaculate, the percentage of pregnant females was calculated separately. The results revealed that the pregnancy rate ranged from 20.0 to 85.7% for heifers and from 7.7 to 66.7% for cows. On the basis of the pregnancy rate (PR) obtained, the ejaculates were divided into 3 groups: high PR (about 25% of ejaculates), medium PR (about 50% of ejaculates) and low PR (about 25% of ejaculates). Significant differences were detected for amplitude of lateral head displacement (ALH) and beat cross frequency (BCF) between high- and low-fertility ejaculates in heifers. Pearson’s correlation analysis showed a significant relationship between the BCF and the pregnancy rate for heifers (r = 0.53, P<0.01) and there was a trend towards significance for ALH (r = −0.37, P = 0.07). There was no relationship between the sperm quality parameters and pregnancy rate of cows. In conclusion, the present study identified markers of sexed bull sperm function that were related to the fertility of inseminated heifers.