摘要
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.
摘要译文
虽然环境和管理方面的变化主要与荷斯坦奶牛在过去25年的繁殖效率下降有关，但男性的生育能力不容忽视。最近测量的阴囊周长，精液数量/质量与1969年荷斯坦公牛报告的数值相当。精液加工的技术进步反映在20世纪90年代后期使用冷冻精液的受精率与20世纪50年代报道的非冷冻精液相比。人工授精（AI）剂量的生育潜力是其中包含的精液的数量，质量和健康状态的函数。对父系健康和相关疾病检测方案的管理至关重要。精液质量评估，每剂量细胞数量的调整，以及射精和/或公牛的剔除，最大限度地减少出售的射精和/或公牛的生育率变化。确定与生育相关的额外精液质量属性可以提供更准确的方法来预测，管理和选择AI生育力。因为大多数已知的精液质量特征的值高度相关，与现有方法相比，任何新技术都必须考虑到所带来的附加效益（改进的生育率预测或实施的经济效用）。解冻后精子存活的持续时间和/或降低获能率可降低对授精时间的敏感性，并且是从男性角度提高生育率的有希望的机会。不幸的是，精液质量和生育率之间的关联通常受到生育率估计的准确性的限制。在同步排卵前≥24小时的固定时间AI可以提供更敏感的模型，从男性或AI角度评估生育能力。由遗传引起的繁殖效率下降的程度存在相当大的争议。通过精液购买决定，
J.M.DeJarnette;C.E.Marshall;R.W.Lenz;D.R.Monke;W.H.Ayars;C.G.Sattler;. Sustaining the Fertility of Artificially Inseminated Dairy Cattle: The Role of the Artificial Insemination Industry[J]. Journal of Dairy Science, 2004,87(Sup): E93-E104