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

Area of Science:

• Animal Science
• Veterinary Medicine
• Sleep Science

Background:

• Sleep and rest are crucial for animal welfare, yet dairy cow sleep remains poorly understood.
• Disruptions in sleep can negatively impact animal health and productivity.
• Understanding sleep in dairy cows is essential for identifying potential welfare issues.

Purpose of the Study:

• To quantify sleep and rest patterns in dairy cows throughout different stages of the lactation cycle.
• To investigate changes in rapid eye movement (REM) sleep, non-rapid eye movement (NREM) sleep, drowsing, and awake states in relation to calving.
• To establish a baseline for sleep research in dairy cattle.

Main Methods:

• Electrophysiological recordings were used to monitor sleep stages in 19 Swedish Red dairy cows.
• Data were collected on 7 occasions: 2 weeks before calving (dry period) and at 2, 7, 13, 22, 37, and 45 weeks after calving (lactation).
• Statistical analysis (PROC MIXED in SAS) was performed to identify significant differences in sleep parameters across lactation stages.

Main Results:

• Total REM sleep duration was significantly shorter 2 weeks after calving compared to the dry period, primarily due to fewer REM sleep bouts.
• Drowsing duration was also reduced in the early stages of lactation (2 and 13 weeks post-calving).
• REM sleep and rumination predominantly occurred at night but were observed during both day and night.

Conclusions:

• The stage of lactation significantly impacts sleep architecture in dairy cows, particularly REM sleep duration.
• Sleep investigations in dairy cattle must account for the lactation cycle to accurately assess sleep patterns.
• These findings provide critical insights into dairy cow welfare and inform future research on sleep and productivity.