A new longitudinal observation study from the Journal of Dairy Science® explores how block calving on New Zealand dairy farms impacts sleep quantity, quality, and overall stress

Philadelphia, February 27, 2025 – Sleep is as important to humans as food and water, but it is often sacrificed to work, especially for farm workers. Dairy farming, in particular, can involve long hours and substantial physical activity, especially on farms that practice block calving—when cows in a herd all calve during a set period of time, usually over six to 12 weeks. Research into how these management practices affect the sleep quality of farm workers is extremely limited. A recent article in the Journal of Dairy Science documents how researchers in New Zealand are working to fill in the research gaps, illustrating that dairy farmers’ are generally getting less sleep and experiencing more stress during spring calving season—and highlighting ways farms can combat these trends.

Lead investigator Lucy Hall, PhD, of DairyNZ Ltd., explained “Because dairy farmers work around machinery and large animals, sleep deprivation can have serious implications for their health and safety. These people often work in isolated situations, which only increases the risks.”

Cows on pasture must also be moved from pasture to milking parlor, which means greater direct interaction between humans and animals, requiring workers to be alert and careful.

Dr. Hall and her team set out to determine whether farmers working on block-calving, pasture-based dairy farms were getting sufficient sleep quantity and quality over the spring calving period and to identify how factors—including milking frequency, location, and role on the farm—may affect sleep quantity and quality. They enrolled 35 full-time dairy farm workers, aged between 18 and 65, over 90 days corresponding to the spring calving period on 10 farms in New Zealand that milked either once or twice a day.

During the study, the participants were fitted with a sleep activity measuring device—an Oura ring—which shared their sleep data with a corresponding smartphone app. The rings were only worn overnight and recorded total sleep time, sleep efficiency, and the time it took to fall asleep, as well as heart rate measurements, which helped the team measure each worker’s response to stress.

In general, the team discovered that farm workers are not getting enough sleep during the spring calving period, averaging only six hours and 15 minutes per night, lower than the required seven to nine hours for optimal wellbeing and cognitive functioning. Furthermore, from week one to week 13 of the study, the amount of workers’ sleep per night decreased by approximately 48 minutes. However, despite not enough sleep quantity, the workers’ overall sleep quality—including time it took them to fall asleep and amount of time spent asleep—was within the normal range reported in similar studies.

According to Dr. Hall, “Our heart rate data for participants was high compared with normal, healthy adults, indicating that farmers may be stressed over the spring calving period, although it’s not clear how much this increased stress impacts their total sleep time.”

The team also investigated what management practices might impact worker sleep and hypothesized that the farms that milked once daily—versus twice a day—would open up time in the afternoon during which workers might rest.

Dr. Hall explained, “Although we expected once-a-day milking might allow for shorter working days, and therefore, more sleep, we did not factor in other aspects of management on the farm.”

The research found that the available time was instead used for other farm activities, such as working with dry stock, separately milking newly calved cows, or managing the crop wintering of their dry cows, all activities that were not occurring on the farms that milked twice daily.

Additionally, the data showed that each worker’s role on the farm and the farm’s location were more likely to significantly affect workers’ sleep quality and their overall stress response.

Dr. Hall clarified, “We found that that our participants from the West Coast of New Zealand slept less and had higher stress responses, possibly due to their isolated location from larger cities which may impact their ability to recruit staff, resulting in understaffing and a greater workload for those working on farm.”

West Coast farmers also generally milked more cows, and the region experienced a higher than normal rainfall during the study period, all increasing the workload over calving season.

A farm worker’s specific role on the farm also impacted their sleep data, with managers going to bed earlier and showing a lower heart rate compared with the other members of staff.

Says Dr. Hall, “We think this is mostly due to the age differences between farm roles considering that managers are usually older with other staff members trending younger. Young staff may get less sleep since they are prioritizing socializing after work over the amount of sleep they get.”

Overall, the study points out that dairy farmers may be getting less sleep than is ideal for their health during calving and experience increased physiological stress during the calving period.

Dr. Hall commented, “We hope this kind of research emphasizes that dairy farms should ensure a sufficient gap between work ending and starting again.”

This may entail adjusting rosters, better delegation and prioritization of tasks, education on the role of sleep on human health, the integration of certain technologies, or even hiring additional workers.

Dr. Hall and the team were quick to clarify that this initial study is not without its limitations and that larger studies will be needed to draw more conclusions. However, the results do provide important insights into dairy farmers’ sleep.

Dr. Hall added, “In other studies, a lack of sleep has been strongly associated with an increase in accidents and serious errors, and the nature of the work of dairy farming makes such lapses potentially quite serious.”

Prioritizing worker sleep ultimately benefited the worker, the farm, and the cows.