In the dairy cow, negative energy balance affects milk yield and composition as well as animal health. Studying the effects of negative energy balance on dairy cow milk production is thus essential. Feed restriction (FR) experiments attempting to reproduce negative energy balance by reducing the quantity or quality of the diet were conducted in order to better describe the animal physiology changes. The study of FR is also of interest since with climate change issues, cows may be increasingly faced with periods of drought leading to a shortage of forages. The aim of this article is to review the effects of FR during lactation in dairy cows to obtain a better understanding of metabolism changes and how it affects mammary gland activity and milk production and composition. A total of 41 papers studying FR in lactating cows were used to investigate physiological changes induced by these protocols. FR protocols affect the entire animal metabolism as indicated by changes in blood metabolites such as a decrease in glucose concentration and an increase in non-esterified fatty acid or β-hydroxybutyrate concentrations; hormonal regulations such as a decrease in insulin and insulin-like growth factor I or an increase in growth hormone concentrations. These variations indicated a mobilization of body reserve in most studies. FR also affects mammary gland activity through changes in gene expression and could affect mammary cell turnover through cell apoptosis, cell proliferation, and exfoliation of mammary epithelial cells into milk. Because of modifications of the mammary gland and general metabolism, FR decreases milk production and can affect milk composition with decreased lactose and protein concentrations and increased fat concentration. These effects, however, can vary widely depending on the type of restriction, its duration and intensity, or the stage of lactation in which it takes place. Finally, to avoid yield loss and metabolic disorders, it is important to identify reliable biomarkers to monitor energy balance.

中文翻译：

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限食对奶牛产奶量的影响：综述

在奶牛中，负能量平衡会影响产奶量和成分以及动物健康。因此，研究负能量平衡对奶牛产奶的影响至关重要。为了更好地描述动物生理变化，进行了限食 (FR) 实验，试图通过减少饮食的数量或质量来重现负能量平衡。FR 的研究也很有趣，因为随着气候变化问题，奶牛可能会越来越多地面临导致草料短缺的干旱时期。本文的目的是回顾 FR 在奶牛泌乳期间的影响，以便更好地了解新陈代谢变化以及它如何影响乳腺活动以及产奶量和成分。共有 41 篇研究泌乳奶牛 FR 的论文被用来研究这些协议引起的生理变化。FR 方案影响整个动物代谢，如血液代谢物的变化所示，例如葡萄糖浓度的降低和非酯化脂肪酸或 β-羟基丁酸浓度的增加；激素调节，例如胰岛素和胰岛素样生长因子 I 的减少或生长激素浓度的增加。在大多数研究中，这些变化表明身体储备的动员。FR 还通过基因表达的变化影响乳腺活动，并可能通过细胞凋亡、细胞增殖和乳腺上皮细胞脱落进入乳汁来影响乳腺细胞更新。由于乳腺和一般新陈代谢的改变，FR 会降低牛奶产量，并会影响牛奶成分，降低乳糖和蛋白质浓度，增加脂肪浓度。然而，这些影响可能因限制的类型、持续时间和强度或发生的泌乳阶段而有很大差异。最后，为了避免产量损失和代谢紊乱，重要的是要确定可靠的生物标志物来监测能量平衡。