Relationship between sperm apoptosis and bull fertility: in vivo and in vitro studies.

The objectives of this study were to confirm the relationship of apoptosis-associated membrane and nuclear changes in bull spermatozoa with field fertility, to predict the fertility of beef bulls used for natural breeding and to study the role of DNA-nicked spermatozoa in early embryonic development. In Experiment 1, the relationship between fertility and different sperm populations identified by the Annexin V/propidium iodide (PI) and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assays was determined. Bull fertility was related to live (PPPin vitro cleavage and blastocyst rates was evaluated, using 30000 or 300000 spermatozoa per droplet. Cleavage rate was adversely affected (PP<0.05) in high DNA-nicked spermatozoa at the lower sperm concentration. In conclusion, the incidence of DNA-nicked spermatozoa is a useful marker to predict a bull's fertility potential. DNA-nicked spermatozoa showed adverse effects on early embryonic development.