Niu M, Ying Y, Bartell P A, Harvatine K J
Department of Animal Science, Penn State University, University Park, PA16802.
Department of Animal Science, Penn State University, University Park, PA16802.
J Dairy Sci. 2014 Dec;97(12):7764-76. doi: 10.3168/jds.2014-8261. Epub 2014 Oct 11.
The timing of feed intake entrains circadian rhythms regulated by internal clocks in many mammals. The objective of this study was to determine if the timing of feeding entrains daily rhythms in dairy cows. Nine Holstein cows were used in a replicated 3 × 3 Latin square design with 14-d periods. An automated system recorded the timing of feed intake over the last 7 d of each period. Treatments were feeding 1×/d at 0830 h (AM) or 2030 h (PM) and feeding 2×/d in equal amounts at 0830 and 2030 h. All treatments were fed at 110% of daily intake. Cows were milked 2×/d at 0500 and 1700 h. Milk yield and composition were not changed by treatment. Daily intake did not differ, but twice-daily feeding tended to decrease total-tract digestibility of organic matter and neutral detergent fiber (NDF). A treatment by time of day interaction was observed for feeding behavior. The amount of feed consumed in the first 2h after feeding was 70% greater for PM compared with AM feeding. A low rate of intake overnight (2400 to 0500 h; 2.2 ± 0.74% daily intake/h, mean ± SD) and a moderate rate of intake in the afternoon (1200 to 1700 h; 4.8 ± 1.1% daily intake/h) was noted for all treatments, although PM slightly reduced the rate during the afternoon period compared with AM. A treatment by time of day interaction was seen for fecal NDF and indigestible NDF (iNDF) concentration, blood urea nitrogen, plasma glucose and insulin concentrations, body temperature, and lying behavior. Specifically, insulin increased and glucose decreased more after evening feeding than after morning feeding. A cosine function within a 24-h period was used to characterize daily rhythms using a random regression. Rate of feed intake during spontaneous feeding, fecal NDF and iNDF concentration, plasma glucose, insulin, NEFA, body temperature, and lying behavior fit a cosine function within a 24-h period that was modified by treatment. In conclusion, feeding time can reset the daily rhythms of feeding and lying behavior, core body temperature, fecal NDF and iNDF concentration, and plasma blood urea nitrogen, glucose, and insulin concentration of dairy cows, but has no effect on daily DMI and milk production.
在许多哺乳动物中，采食时间会影响由内部生物钟调节的昼夜节律。本研究的目的是确定采食时间是否会影响奶牛的日节律。选用9头荷斯坦奶牛，采用重复的3×3拉丁方设计，每期14天。自动化系统记录每个周期最后7天的采食时间。处理方式为：每天0830时（上午）或2030时（下午）采食1次，以及在0830时和2030时等量采食2次。所有处理的采食量均为每日摄入量的110%。奶牛每天0500时和1700时挤奶2次。产奶量和乳成分不受处理方式的影响。日采食量没有差异，但每日两次采食倾向于降低有机物和中性洗涤纤维（NDF）的全消化道消化率。观察到采食行为存在处理方式与时间的交互作用。与上午采食相比，下午采食后前2小时的采食量高出70%。所有处理方式下，夜间（2400至0500时）采食率较低（2.2±0.74%每日摄入量/小时，均值±标准差），下午（1200至1700时）采食率适中（4.8±1.1%每日摄入量/小时），不过与上午相比，下午采食略微降低了采食率。观察到粪便NDF和不可消化NDF（iNDF）浓度、血尿素氮、血浆葡萄糖和胰岛素浓度、体温及躺卧行为存在处理方式与时间的交互作用。具体而言，晚间采食后胰岛素升高幅度和葡萄糖降低幅度均大于早晨采食后。使用随机回归分析，采用24小时周期内的余弦函数来表征日节律。自发采食期间的采食率、粪便NDF和iNDF浓度、血浆葡萄糖、胰岛素、非酯化脂肪酸（NEFA）、体温及躺卧行为在24小时周期内符合余弦函数，且受处理方式影响。总之，采食时间可重置奶牛采食和躺卧行为、核心体温、粪便NDF和iNDF浓度以及血浆血尿素氮、葡萄糖和胰岛素浓度的日节律，但对每日干物质摄入量和产奶量无影响。
