The importance of rest and sleep is well established; we know, for example, that lack of sleep impairs immune function in rats and increases pain sensitivity in humans. However, little is known about sleep in dairy cows, but a lack of rest and sleep is discussed as a possible welfare problem in cattle. A first step toward a better understanding of sleep in dairy cows is to quantify the time cows spend awake and asleep in different stages of lactation. Using electrophysiological recordings on 7 occasions in wk -2, 2, 7, 13, 22, 37, and 45 in relation to calving, we investigated changes in rapid eye movement (REM) sleep time as well as non-rapid eye movement (NREM) sleep, drowsing, awake, and rumination in 19 dairy cows of the Swedish Red breed kept in single pens with ad libitum access to feed and water. The recordings on wk -2 and 45 were conducted during the dry period, and all others during lactation. The PROC MIXED procedure in SAS (SAS Institute Inc., Cary, NC) was used to test for significant differences in REM, NREM, drowsing, awake, and rumination between the different stages of lactation cycle. Pairwise comparisons between all recording occasions showed that total REM sleep duration was shorter for cows in wk 2 relative to calving compared with wk -2, and the number of REM sleep bouts were fewer in wk 2 compared with wk -2. The REM sleep was recorded during both the day (0500-2100 h) and night (2100-0500 h), but predominantly performed at night compared with daytime, and the bout duration was longer during nighttime compared with daytime. A tendency was observed for time spent in NREM sleep to be shorter in wk 2 relative to calving compared with wk -2. The duration spent drowsing was shorter for cows in wk 2 and 13 relative to calving compared with wk -2. We found no effect of stage of lactation cycle on the duration of awake or ruminating. Our study is the first to assess sleep distribution during a lactation cycle, and our results show that stage of lactation is important to consider when moving forward with sleep investigations in dairy cows. The shortest REM sleep duration was found for cows 2 wk after calving and longest 2 wk before calving, and the difference was due a higher number of REM sleep bouts in the recording 2 wk before calving. The REM sleep and rumination predominantly occurred at night but were recorded during both day and night.

In human sleep studies, the probability of discomfort from the electrodes and the change in environment usually results in first-night recordings being discarded. Sleep recordings from the first night in human subjects often differ in amount of REM (rapid eye movement) sleep and the overall sleep architecture. This study investigated whether recordings of sleep states in dairy cows also show a first-night effect. Non-invasive electrophysiological recordings were carried out on nine cows of the Swedish Red breed during three consecutive 24-hour periods (recording days 1–3). Overall, cows spent 12.9 ± 1.4 hours awake, 8.2 ± 1 hours ruminating, 57.2 ± 20.3 min drowsing, 44.1 ± 20.2 min in REM sleep and 64.3 ± 38.1 min in NREM (non-rapid eye movement) sleep (mean ± SD) and there were no significant differences between recording days in total duration for any of the sleep and awake states. However, the bouts of REM sleep and rumination were longer, and the awake bouts were shorter, at night time compared to daytime, regardless of recording day. The awake bouts also showed an interaction effect with longer bouts at daytime during day 1 compared to daytime on day 3. Data on sleep and awake states recorded in adult dairy cows during three consecutive 24-h periods showed great variation in sleep time between cows, but total time for each state was not significantly affected by recording day. Further and more detailed studies of how sleep architecture is affected by recording day is necessary to fully comprehend the first-night effect in dairy cows.

The most suitable light intensity for cows during nighttime has not been thoroughly investigated. Recommendations on the night-time lighting regimen on dairy farms differ between countries and range from light throughout the night to darkness to allow the animals a rest from artificial light. Commercial actors recommend red light for night-time lighting in cattle barns to facilitate livestock supervision with minimum disturbance for the animals. However, little is known about how light intensity, spectrum, and uniformity affect the ability of cows to navigate their indoor environment. Thus, in a change-over study with 12 pregnant, nonlactating dairy cows, we observed how the cows walked through an obstacle course under different light treatments. Obstacles were positioned differently for every run, to present a novel challenge for each light environment. Fourteen different light treatments were tested, involving intensity ranging from <0.01 (darkness) to 4.49 µmol m^-2 s^-1, high or low uniformity, and white or red color. Light was characterized in terms of illuminance, photon flux density, spectral composition, and uniformity. Additionally, assessment of the environmental light field was used to describe each lighting condition from a bovine and human perspective. Data were analyzed in a generalized mixed model to assess whether lighting conditions affected cow walking speed or stride rate. Pair-wise post hoc comparisons showed that the cows walked at a slower speed in nonuniform red light compared with uniform white light or uniform red light. Interestingly, darkness did not alter walking speed or stride rate. The odds of different behaviors occurring were not affected by lighting conditions. In conclusion, darkness did not affect the ability of cows to navigate through the obstacle course, but medium-intensity, nonuniform red light affected their speed. Hence, cows do not necessarily need night-time lighting to navigate, even in a test arena with obstacles blocking their way, but nonuniform light distribution may have an effect on their movements.

Sensors are increasingly being used to monitor animal behaviour. Data handling methods have, however, lagged behind the continuous data stream to some extent, often being limited to summarizing data into daily averages at group level. This research reflection presents our opinion of the neglected application of 24-h pattern analysis. Recent studies of dairy cow behaviour have demonstrated that additional ways of analysing data improve our understanding of animal behaviour and add value to data that were already retrieved. The terminology for the described 24-h patterns differs between these studies, making them difficult to compare. Thus, diurnal, circadian, daily, periodicity and 24-h pattern are all terms used to describe dairy cow activities over a 24-h period. Several studies have shown that the 24-h behavioural pattern at herd level is relatively consistent over time, and that with well-established management routines, a specific herd signature will be evident. However, within a herd, individual cows may have individual 24-h patterns with more or less variability. Recent studies suggest that deviations from herd and/or individual 24-h patterns can be used to describe cow robustness, as well as to predict disease. We strongly believe that individual and herd 24-h patterns provide a great deal of information about behaviour and that these patterns offer opportunity for more precise and timely health management and welfare monitoring.

Sleep serves several essential functions in all mammals including dairy cattle. Researchers are beginning to estimate sleep in dairy cattle using a combination of physiological measurements (e.g., polysomnography) as well as changes in behavior (e.g., different resting postures). Sleep may provide unique insight into how cows and calves respond to, and cope with, their environments, as a complement to other common measurements such as lying time. Although each of the methods to assess sleep in cattle has its advantages, there remain several challenges with each approach. The objective of this narrative mini-review is to describe current methods for estimating sleep in dairy cattle, including some of the advantages and limitations with each method. We will start with describing the research to date on adult cows, followed by preweaning dairy calves. We end the review with recommendations for researchers interested in assessing sleep in dairy cattle and ideas for future areas of research.

This research communication describes how different detachment levels (0.48, 0.3 and 0.06 kg milk/min) at the quarter-level affect milk flow profiles and overall milking efficiency in automatic milking systems. We hypothesized a higher detachment level would result in greater mean flow rates without affecting the volume of harvested milk per cow during 24 h compared to lower detachment levels. The data suggest milk flow decreased to a rate below the overmilking limit within the 6-s delay time required for termination in all treatments, but the duration of overmilking was shorter for the greatest detachment level compared to the other treatments. We conclude that setting a detachment level at a greater milk flow rate reduces the duration of overmilking without affecting the amount of milk harvested when applied to cows in mid-lactation during quarter-level milking. We also suggest that the steepness of the decline phase of the milk flow curve might have a larger effect than the actual detachment level on the duration of overmilking.