Teagasc, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy P61 P302, Co. Cork, Ireland.
J Dairy Sci. 2021 Apr;104(4):3789-3819. doi: 10.3168/jds.2020-19519. Epub 2021 Mar 2.
Because a growing proportion of the beef output in many countries originates from dairy herds, the most critical decisions about the genetic merit of most carcasses harvested are being made by dairy producers. Interest in the generation of more valuable calves from dairy females is intensifying, and the most likely vehicle is the use of appropriately selected beef bulls for mating to the dairy females. This is especially true given the growing potential to undertake more beef × dairy matings as herd metrics improve (e.g., reproductive performance) and technological advances are more widely adopted (e.g., sexed semen). Clear breed differences (among beef breeds but also compared with dairy breeds) exist for a whole plethora of performance traits, but considerable within-breed variability has also been demonstrated. Although such variability has implications for the choice of bull to mate to dairy females, the fact that dairy females themselves exhibit such genetic variability implies that "one size fits all" may not be appropriate for bull selection. Although differences in a whole series of key performance indicators have been documented between beef and beef-on-dairy animals, of particular note is the reported lower environmental hoofprint associated with beef-on-dairy production systems if the environmental overhead of the mature cow is attributed to the milk she eventually produces. Despite the known contribution of beef (i.e., both surplus calves and cull cows) to the overall gross output of most dairy herds globally, and the fact that each dairy female contributes half her genetic merit to her progeny, proxies for meat yield (i.e., veal or beef) are not directly considered in the vast majority of dairy cow breeding objectives. Breeding objectives to identify beef bulls suitable for dairy production systems are now being developed and validated, demonstrating the financial benefit of using such breeding objectives over and above a focus on dairy bulls or easy-calving, short-gestation beef bulls. When this approach is complemented by management-based decision-support tools, considerable potential exists to improve the profitability and sustainability of modern dairy production systems by exploiting beef-on-dairy breeding strategies using the most appropriate beef bulls.
由于许多国家的牛肉产量越来越多地来自奶牛群，因此大多数被收获的胴体的遗传优势的最关键决策是由奶牛生产者做出的。人们对从奶牛雌性中产生更有价值的小牛的兴趣正在加剧，而最有可能的手段是使用经过适当选择的肉牛公牛与奶牛雌性交配。考虑到随着牛群指标的提高（例如繁殖性能）和技术进步的更广泛采用（例如，性别鉴定精液），可以进行更多的牛肉×奶牛交配，这种情况尤其如此。在一系列性能特征方面，牛肉品种之间（以及与奶牛品种相比）存在明显的品种差异，但也证明了品种内存在相当大的变异性。尽管这种变异性对选择与奶牛雌性交配的公牛有影响，但奶牛雌性本身表现出这种遗传变异性意味着“一刀切”可能不适合公牛选择。尽管已经记录了牛肉和牛犊之间的一系列关键性能指标之间的差异，但值得注意的是，如果将成年奶牛的环境开销归因于她最终生产的牛奶，那么与牛犊生产系统相关的较低的环境足迹。尽管已知牛肉（即多余的小牛和淘汰牛）对全球大多数奶牛群的总毛收入有贡献，并且每个奶牛雌性将其一半的遗传优势贡献给她的后代，但肉类产量的代表（即小牛肉或牛肉）并没有直接考虑到绝大多数奶牛育种目标。现在正在制定和验证适合奶牛生产系统的肉牛公牛的选育目标，证明了在关注奶牛公牛或易于产犊、短妊娠期的肉牛公牛之外，使用这些选育目标的经济效益。当这种方法与基于管理的决策支持工具相结合时，通过利用最适合的肉牛公牛来实施牛肉×奶牛的繁殖策略，就有可能显著提高现代奶牛生产系统的盈利能力和可持续性。
