Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bremgartenstrasse 109a, CH-3012 Bern, Switzerland.
J Anim Sci. 2022 Mar 1;100(3). doi: 10.1093/jas/skac044.
Milk production in dairy cows increases worldwide since many decades. With rising milk yields, however, potential limiting factors are increasingly discussed. Particularly, the availability of glucose and amino acids is crucial to maintain milk production as well as animal health. Limitations arise from feed sources, the rumen and digestive tract, tissue mobilization, intermediary metabolism and transport, and the uptake of circulating nutrients by the lactating mammary gland. The limiting character can change depending on the stage of lactation. Although physiological boundaries are prevalent throughout the gestation-lactation cycle, limitations are aggravated during the early lactation period when high milk production is accompanied by low feed intake and high mobilization of body reserves. The knowledge about physiological constraints may help to improve animal health and make milk production more sustainably. The scope of this review is to address contemporary factors related to production limits in dairy cows from a physiological perspective. Besides acknowledged physiological constraints, selected environmental and management-related factors affecting animal performance and physiology will be discussed. Potential solutions and strategies to overcome or to alleviate these constraints can only be presented briefly. Instead, they are thought to address existing shortcomings and to identify possibilities for optimization. Despite a scientific-based view on physiological limits, we should keep in mind that only healthy animals could use their genetic capacity and produce high amounts of milk.
几十年来，奶牛的产奶量在全球范围内不断增加。然而，随着产奶量的提高，潜在的限制因素越来越受到关注。特别是葡萄糖和氨基酸的供应对于维持牛奶产量和动物健康至关重要。限制因素来自饲料来源、瘤胃和消化道、组织动员、中间代谢和运输，以及循环营养物质被泌乳乳腺吸收。限制因素的性质可能因泌乳阶段而异。尽管在妊娠-泌乳周期中普遍存在生理界限，但在泌乳早期，当高牛奶产量伴随着低采食量和大量动员体储备时，限制因素会加剧。了解生理限制的知识可能有助于改善动物健康，使牛奶生产更可持续。本综述的范围是从生理学角度探讨与奶牛生产限制有关的当代因素。除了公认的生理限制外，还将讨论影响动物性能和生理学的选定环境和管理相关因素。克服或缓解这些限制的潜在解决方案和策略只能简要介绍。相反，它们旨在解决现有不足，并确定优化的可能性。尽管我们对生理限制有科学的看法，但我们应该记住，只有健康的动物才能利用其遗传能力并生产大量牛奶。
