Rapid eye movement sleep time in dairy cows changes during the lactation cycle

Abstract

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.

Doing nothing and what it looks like: inactivity in fattening cattle

“…Closed eyes may indicate more sleep on pasture. This would be in line with findings that cattle on pasture have several episodes of rest and sleep during the day (Sambraus, 1971) and that cattle kept indoors mostly sleep at night (Ternman et al, 2019). However, it is important to note that the closure of the eyes alone is not sufficient to define the animals as being asleep and other characteristics that differentiate between sleep and resting (Nicolau et al, 2000) were not recorded in our study.…”

Doing nothing and what it looks like… Inactivity in fattening cattle

“…We did not differentiate between left and right ear when recording asymmetry but given that the asymmetrical ears were the only outcome measure which differed statistically significant between husbandry systems, such a differentiation may be a valuable addition to our Inactivity Ethogram in future studies. The longer time animals on PASTURE spent with closed eyes may indicate that these animals slept more during our observations, which would be in line with findings that cattle on pasture have several episodes of rest and sleep during the day , while cattle kept indoors mostly sleep during the night (Ternman et al, 2019. However, it needs to be stressed that the closure of the eyes alone is not sufficient to define the animals as being asleep; several characteristics have to be fulfilled to properly differentiate between sleep and resting (Nicolau et al, 2000), but those were not recorded in our study.…”

Invited review: Lying time and the welfare of dairy cows

“…However, to date, these methods do generate reliable estimates of REM sleep (Ruckebusch, 1972). In addition, NREM sleep and total time spent sleeping in adult cattle are possible to measure when the animals are not ruminating (Ternman et al, 2012(Ternman et al, , 2014(Ternman et al, , 2018(Ternman et al, , 2019Kull et al, 2019), and the following results are limited by these constraints.…”