The Interaction of Male and Female in Success of Mating

Introduction: To most in this audience, having a veterinary practice dealing with problems associated with reproduction is undoubtedly fun, profitable and rewarding. However, reproductive problems can also be most frustrating, often testing the limits of our knowledge and our patience. From personal experience, I can also say the same for research in reproductive physiology, particularly where we are interested in understanding factors important to reproductive success or identifying causes and remedies for reproductive failure. Since the early 60s, in our lab we sought useful correlations of seminal traits and fertility in order to ultimately predict the reproductive outcome of bovine semen used in artificial breeding or the fertility of a specific male under natural service. Despite these efforts, to this day we can only account for approximately 50% of the variation in fertility among males by measuring seminal traits, leaving the goal of predictability quite unachieved. In our frustration and need to progress in this endeavor, shared by many other reproduction laboratories throughout the world, the fate of sperm in the female reproductive tract (quantitatively and qualitatively) has become an important question needing to be addressed. Answers in response to this question have been enlightening and although they are not "silver bullets" to predicting fertility, they have provided insight to the nature of reproductive success and failure and have exposed the roots of some of our frustrations. I would like to share some of these insights with you today. Hopefully, they may explain some of the frustrations encountered in a therio practice or perhaps offer solutions to the critical eye as new tools become available in control of semen production as well as in the control of ovulation in the female.