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, December 18, 2024 – 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 6 to 12 weeks. Research into how these management practices affect the sleep quality of farm workers is extremely limited. In a recent article in the Journal of Dairy Science, 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.
“Because dairy farmers work around machinery and large animals, sleep deprivation can have serious implications for their health and safety,” says lead investigator Lucy Hall, PhD, of DairyNZ Ltd. “These people often work in isolated situations, which only increases the risks,” she added. Cows on pasture must also be moved from pasture to milking parlor, requiring greater direct interaction between humans and animals, requiring workers to be alert and careful.
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 on their phones. 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.
Caption: Researchers in New Zealand assessed the effect on dairy farmers’ sleep of spring block calving in pasture-based systems. (Credit: DairyNZ)
Overall, the team discovered that farm workers are not getting enough sleep over the spring calving period, averaging only 6 hours and 15 minutes, lower than the required 7 to 9 hours for optimal wellbeing and cognitive functioning. Furthermore, from week 1 to week 13 of the study, workers’ sleep amount 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 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, though 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. 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.” They found that the available time was instead used for other farm activities, such as working with drystock, 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.
Instead, the data showed that each workers’ role on the farm and the farm’s location were more likely to significantly affect workers’ sleep quality and their overall stress response. “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,” explained Hall. West Coast farmers were also generally milking more cows, and experienced a higher than normal rainfall during the study period, all increasing the workload of calving season.
A farm workers’ unique 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. “We think this is mostly due to the age differences between farm roles,” said Hall, “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 over the calving period. “We hope this kind of research emphasizes that dairy farms should ensure a sufficient gap between work ending and starting again,” said Hall. 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.
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 insight into dairy farmers’ sleep. “In other studies, a lack of sleep has been strongly associated with an increase in accidents and serious errors,” Hall added,” and the nature of the work of dairy farming makes such lapses potentially quite serious.” Prioritizing worker sleep is ultimately a benefit for the worker, the farm, and the cows.
Notes for editors
The article is “An exploration into the sleep of workers on block-calving, pasture-based dairy farms,” by Lucy S. Hall, John P. Edwards, Kelly Dale, Victoria Westbrooke, Racheal H. Bryant, Barbara Kuhn-Sherlock, and Callum R. Eastwood (https://doi.org/10.3168/jds.2024-24969). It appears in the Journal of Dairy Science, volume 107, issue 11 (November 2024), published by the American Dairy Science Association and Elsevier.
The article is openly available at https://www.journalofdairyscience.org/article/S0022-0302(24)00980-9/fulltext and the PDF version is available at https://www.journalofdairyscience.org/action/showPdf?pii=S0022-0302%2824%2900980-9.
Full text of this article is also available to credentialed journalists upon request; contact Eileen Leahy at +1 732 406 1313 or jdsmedia@elsevier.com. Journalists wishing to interview the authors should contact the corresponding author, Lucy S. Hall, PhD, DairyNZ Ltd., Lincoln, NZ, at lucy.hall@dairynz.co.nz.
About the Journal of Dairy Science
The Journal of Dairy Science® (JDS), an official journal of the American Dairy Science Association® (ADSA), is co-published by Elsevier and ADSA. It is the leading general dairy research journal in the world. JDS readers represent education, industry, and government agencies in more than 70 countries, with interests in biochemistry, breeding, economics, engineering, environment, food science, genetics, microbiology, nutrition, pathology, physiology, processing, public health, quality assurance, and sanitation. JDS has a 2022 Journal Impact Factor of 3.5 and five-year Journal Impact Factor of 4.2 according to Journal Citation Reports™ (Source: Clarivate™ 2022). www.journalofdairyscience.org
About the American Dairy Science Association (ADSA®)
The American Dairy Science Association (ADSA) is an international organization of educators, scientists, and industry representatives who are committed to advancing the dairy industry and keenly aware of the vital role the dairy sciences play in fulfilling the economic, nutritive, and health requirements of the world’s population. It provides leadership in scientific and technical support to sustain and grow the global dairy industry through generation, dissemination, and exchange of information and services. Together, ADSA members have discovered new methods and technologies that have revolutionized the dairy industry.www.adsa.org
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