Researchers in Denmark report cow sleep patterns change across lactation cycle, according to a study published in the June 2019 issue of Journal of Dairy Science. Cows were monitored two weeks before calving, as well as at weeks two, seven, 13, 22, 37 and 45 after calving. Cows had the longest duration of deep sleep, known as rapid eye movement (REM), two weeks before calving and had the shortest REM duration two weeks after calving.
Lack of sleep may be considered an animal welfare concern, and scientists hope to lay the foundation for future research. A previous study by the authors published by Public Library of Science ONE in 2017 found REM sleep is part of a larger daily rhythm in dairy cattle. Cows spent about one hour in REM sleep in contrast to 13 hours awake, eight hours ruminating, one hour drowsing and one hour in non-rapid eye movement sleep, according to the 2017 study.
A variety of factors may influence sleep. Cattle in the 2019 study were housed at different farms and exposed to different management routines. While the timing of sleep differed among farms, the overall duration of sleep remained similar, suggesting management routine did not influence total sleep hours. Rather, differences in sleep over the lactation cycle may be influenced by cows’ day-to-day needs.
One theory as to why lactating cows sleep less is they spend less time lying down and more time standing to eat and be milked compared to dry cows, according to past research cited by the 2019 study. Furthermore, because feedings typically occur during the day, authors explained this may be why REM sleep primarily occurred at night in their 2019 study. Rumination was also measured by researchers, but no change was observed across the lactation cycle.
As the dairy industry continues to provide the best husbandry conditions possible, it is important to not disregard the importance of sleep. This is an emerging research topic and could have long-term impacts on dairy farm management in years to come.