Kuhn M T, Hutchison J L
Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350, USA.
J Dairy Sci. 2008 Jun;91(6):2481-92. doi: 10.3168/jds.2007-0743.
The objectives of this research were to assess the utility of multiple services, rather than first service only, and an expanded service sire term for prediction of bull conception rate (CR) by artificial insemination in the United States. The intent with the expanded service sire term was to determine whether accuracy could be improved by estimating factors affecting the bull's CR explicitly in the model and then formulating the bull's prediction as the sum of his own service sire solution along with the solutions for the other factors. Factors considered for the expanded service sire term included age of the bull at the time of mating, stud, inbreeding of the service sire, inbreeding of the mating (potential embryo), and an additive genetic effect. Both simulated and field data were used to study the objectives. In simulation, predictions were compared with true values, whereas with real data, predictions were compared with the bulls' average CR in set-aside data. Field data, using lactations 1 to 5, included 3,312,998 breedings of 737,626 Holstein cows in 1,419 herds distributed over 43 states and across 12 yr (1995 to 2006). The use of both multiple services and an expanded service sire term improved the accuracy of predictions. Multiple services contributed a 7 to 9% increase in accuracy, whereas the expanded service sire term improved accuracy by an estimated 12%. The amount of improvement in accuracy depends on the number of services available, but even for bulls with at least 500 matings, the combination of multiple services and an expanded service sire term can be expected to result in an overall increase in accuracy of at least 20%. Mean differences between predictions and bulls' average CR in set-aside data indicated that this improvement in accuracy can be brought about without introducing bias into the evaluations. Heritability estimates for artificial-insemination bull CR were essentially zero. Thus, use of an additive genetic effect for the service sire will not be of assistance in predicting bull fertility. All 4 of the other factors used in the expanded service sire term contributed to improved accuracy, although age of the bull at the time of mating was, by far, the major factor (correlation of 55.2% with future-year CR when included, 44.0% when not included). Allowing the stud effect to vary by year and using only the stud's most recent year solution in prediction were shown to be superior to using stud alone.
本研究的目的是评估多种服务（而非仅首次服务）以及一个扩展的种公牛术语对预测美国人工授精公牛受胎率（CR）的效用。扩展种公牛术语的目的是确定在模型中明确估计影响公牛CR的因素，然后将公牛的预测值表示为其自身种公牛解与其他因素解之和，是否能提高预测准确性。扩展种公牛术语所考虑的因素包括配种时公牛的年龄、种畜场、种公牛的近交系数、配种（潜在胚胎）的近交系数以及加性遗传效应。模拟数据和实际数据均用于研究这些目标。在模拟中，将预测值与真实值进行比较，而对于实际数据，将预测值与预留数据中公牛的平均CR进行比较。实际数据使用第1至5胎次的数据，包括分布在43个州的1419个牛群中737626头荷斯坦奶牛的3312998次配种（1995年至2006年，共12年）。使用多种服务和扩展种公牛术语提高了预测的准确性。多种服务使准确性提高了7%至9%，而扩展种公牛术语使准确性提高了约12%。准确性提高的幅度取决于可用服务的数量，但即使对于配种次数至少为500次的公牛，多种服务和扩展种公牛术语的组合预计也会使总体准确性至少提高20%。预测值与预留数据中公牛平均CR之间的平均差异表明，这种准确性的提高不会在评估中引入偏差。人工授精公牛CR的遗传力估计值基本为零。因此，在种公牛中使用加性遗传效应无助于预测公牛的繁殖力。扩展种公牛术语中使用的其他4个因素均有助于提高准确性，尽管配种时公牛的年龄是迄今为止的主要因素（包含该因素时与未来年份CR的相关性为55.2%，不包含时为44.0%）。允许种畜场效应随年份变化，并在预测中仅使用种畜场最近一年的解，被证明优于仅使用种畜场。
