Sperm binding to epithelial oviduct explants in bulls with different nonreturn rates investigated with a new in vitro model

A new in vitro method was developed for analyzing the capacity of sperm to bind to oviductal epithelium to determine whether this binding capacity could be used to predict nonreturn rates (NRR). Sperm binding was evaluated by counting 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbo-cyanine iodide (JC-1)-labeled spermatozoa attached to oviductal epithelium and by measuring the surface area of the oviduct explants by means of an image analysis program. Hepes + Tyrode albumin lactate pyruvate (TALP) was a more useful medium than in vitro fertilization (IVF)-TALP, TCM-199 medium + 10% fetal calf serum, and TCM-199 medium alone for the investigation of sperm binding to oviductal explants. Oviduct explants with a surface area of <20000 mum(2) provided more consistent results than did explants with a surface area of >100000 mum(2). A positive association was found between the log, transformed number of spermatozoa bound to 0.1 mm(2) oviductal epithelium and the NRR of the respective sires after 24 h of coincubation, provided that the membrane integrity of the sperm sample was >60%. Determination of the capacity of sperm to bind to oviductal explants could become a reliable in vitro method for predicting the NRR of a given sire.