The timing of feed intake can alter circadian rhythms of peripheral tissues. Milk synthesis displays a daily rhythm across several species, but the effect of feeding time on these rhythms is poorly characterised. The objective of this experiment was to determine if the time of feed intake modifies the daily patterns of milk synthesis, plasma metabolites and body temperature in dairy cows. Sixteen lactating Holstein dairy cows were randomly assigned to one of the two treatment sequences in a cross-over design with 17 d periods. Treatments included day-restricted feeding (DRF; feed available from 07.00 to 23.00 hours) and night-restricted feeding (NRF; feed available from 19.00 to 11.00 hours). Cows were milked every 6 h on the last 7 d of each period, and blood samples were collected to represent every 4 h over the day. Peak milk yield was shifted from morning in DRF to evening in NRF, while milk fat, protein and lactose concentration peaked in the evening in DRF and the morning in NRF. Plasma glucose, insulin, NEFA and urea nitrogen concentration fit daily rhythms in all treatments. Night feeding increased the amplitude of glucose, insulin and NEFA rhythms and shifted the daily rhythms by 8 to 12 h (P < 0·05). Night feeding also phase-delayed the rhythm of core body temperature and DRF increased its amplitude. Altering the time of feed availability shifts the daily rhythms of milk synthesis and plasma hormone and metabolite concentrations and body temperature, suggesting that these rhythms may be entrained by food intake.

中文翻译：

---

与白天限饲相比，夜间限饲奶牛的采食量、乳汁合成和血浆代谢的日节律发生改变

采食时间可以改变外周组织的昼夜节律。多个物种的乳汁合成表现出每日节律，但喂养时间对这些节律的影响尚不清楚。该实验的目的是确定采食时间是否会改变奶牛的每日牛奶合成、血浆代谢和体温模式。将 16 头泌乳荷斯坦奶牛随机分配至采用 17 天交叉设计的两种处理序列之一。治疗包括白天限制喂养（DRF；07:00 至 23:00 提供喂养）和夜间限制喂养（NRF；19:00 至 11:00 提供喂养）。每个时期的最后 7 天，每 6 小时对奶牛挤奶一次，并采集血液样本以代表当天每 4 小时。产奶量峰值从 DRF 的早晨转移到 NRF 的晚上，而乳脂、蛋白质和乳糖浓度在 DRF 的晚上达到峰值，而 NRF 的早晨则达到峰值。在所有治疗中，血浆葡萄糖、胰岛素、NEFA 和尿素氮浓度均符合每日节律。夜间喂养增加了葡萄糖、胰岛素和 NEFA 节律的幅度，并将每日节律改变了 8 至 12 小时（磷< 0·05)。夜间喂食还延迟了核心体温的节律，并且 DRF 增加了其幅度。改变饲料供应时间会改变乳汁合成、血浆激素和代谢物浓度以及体温的每日节律，这表明这些节律可能受到食物摄入的影响。