Sustaining the fertility of artificially inseminated dairy cattle: The role of the artificial insemination industry

Abstract

Although changes in environment and management are primarily implicated for the decline in reproductive efficiency of Holstein cows during the past 25 yr, fertility of the male must not be overlooked. Recent measures of scrotal circumference, semen quantity/quality are comparable to values reported for Holstein sires in 1969. Technological advances in semen processing are reflected in fertilization rates using cryopreserved semen in the late 1990s comparable to those reported for non-frozen semen in the 1950s. The fertility potential of an artificial insemination (AI) dose is a function of the quantity, quality, and health status of the semen contained therein. Management of sire health and associated disease testing protocols are paramount. Semen quality evaluations, adjustments to cell numbers per dose, and culling of ejaculates and/or bulls, minimize variation in fertility among ejaculates and/or sires released for sale. Identification of additional semen quality attributes associated with fertility may provide more accurate methods to predict, manage, and select for AI sire fertility. Because the values of most known semen quality traits are highly correlated, any new technology must be considered with respect to the additive benefit imparted compared to existing methodologies (improved fertility prediction or economic utility of implementation). Cryopreservation techniques that extend the duration of post-thaw sperm survival and/or reduce rates of capacitation may reduce sensitivity to insemination timing and are promising opportunities to improve fertility from the male perspective. Unfortunately, the association between semen quality and fertility is usually limited by the accuracy of the fertility estimate. Fixed-time AI ≥ 24. h prior to synchronized ovulation may provide a more sensitive model to evaluate fertility from the male or AI perspective. The role of the AI industry representative has and will continue to evolve from that of salesperson and genetic advisor to that of a reproductive and herd-management consultant. The magnitude of the decline in reproductive efficiency attributable to genetics is of considerable debate. Through semen purchasing decisions, dairy producers largely dictate the relative importance of various genetic traits to the industry and thereby the emphasis that should be placed on these traits in AI sire-sampling programs. © 2004 American Dairy Science Association.