The number of hours of light turkeys and broiler chickens are reared under affects their health and behavior in numerous ways, often negatively, so optimal light management is a key factor in ensuring positive bird welfare and good market weight. A recent study indicating these findings also noted that specific research on turkeys in this area and others is sorely lacking.
Research on turkeys is lacking
Turkeys and broiler chickens are two distinct animals with their own unique characteristics. Yet, research on broilers is often applied to commercial turkeys, which may lead to unexpected effects of management practices related to turkeys.
In addressing this topic at the 2025 Poultry Science Association annual meeting, Karen Schwean-Lardner, PhD, University of Saskatchewan, noted that research on turkeys has been sorely lacking. In a recent literature search she did regarding studies on turkeys and lighting, she found 20 to 30 papers that were published in the ‘90s, approximately 10 in the early 2000s, then very few since.
She posited four reasons for the dearth of research on turkeys: expense, difficulty, equipment needs and declining consumption in some areas of the world. Regarding expense, three broiler trials can be run in the time it takes to run one turkey trial; meanwhile, turkey poults are expensive, so if a bird dies, it’s not a cheap loss.
Running trials with turkeys is also more difficult than with broilers because turkeys are so big, strong and heavy. Since it is often difficult to find funding for loaders in small research trials, people may have to hand carry the 3,000 to 4,000 birds onto a truck, which their size and strength make challenging.
The third barrier is that turkeys require different equipment depending on their age, so the equipment must be changed from small to large during one research trial, or the turkeys have to move to different houses — for example, from a brooding/early rearing barn to a rearing barn for the latter part of production.
Finally, fewer studies are done on turkeys because turkey tends to be seen as a holiday food rather than a staple readily available, like chickens, at fast-food restaurants like McDonald’s.
Commercial turkeys are similar to wild ones
Schwean-Lardner explained that there are similarities between commercial turkeys and wild turkeys which helped guide her research. She noted that “while the percentage of time of specific behaviors may change between wild and commercial turkeys, the behaviors themselves remain the same.”
Wild turkeys live in small groups with one male and a few females. They spend time foraging for food, dust bathing and preening. They are omnivorous to the point they have eaten mercury thermometers and string.
They are ground dwelling except they climb in stages to roost in trees for safety and to hatch their young. This knowledge of how they roost in stages can be applied to enrichment in commercial houses by offering them staged perches versus one high one, Schwean-Lardner said.
Young turkeys can fly at 5 weeks and are usually chased out of the nest by 12 weeks. Males form banded groups and display their feathers in courtship dances.
Effect of lighting periods studied
Schwean-Lardner and her team at the University of Saskatchewan conducted a study of the effects of photoperiod lengths on the behaviors of turkeys and broilers. The overall purpose was to provide information that could be used in the proper management of commercial turkeys rather than focusing on comparing turkeys to broilers.
For the study, both turkeys and broilers were housed in the same facility and subjected to the same lighting treatments, staff and management style. Hank Classen, PhD, originally designed this facility for a lighting research project decades previously.
The experiments exposed the birds to four different light periods — 14, 17, 20 and 23 hours of light per day — and were replicated to ensure validity. The exposures were done four times on approximately 28,000 broilers but only twice on turkeys — 480 toms and 720 hens — due to the higher costs of working with turkeys.
The broilers were housed to 49 days of age while the turkeys were 126 days old at time of shipment. Birds were managed as per Aviagen recommendations, and data were collected throughout on growth, feed intake, mortality and morbidity, and welfare assessments.
The study researchers took video of the birds 24 hours a day at two ages and noted the behavior of every bird every 10 minutes throughout those periods.
More light equals less activity
The length of the photoperiod clearly affected the activity levels of both broilers and turkeys. For both species, longer daylight hours caused them to be inactive, so that at 23 hours, they displayed a “significant increase in doing nothing but laying in the litter.”
For the broilers, this meant spending more than 85% of their time resting with 23 hours of light, which reduced to less than 70% of time resting under 17 and 14 hours of light. This lack of activity can affect numerous areas like feed intake, footpad lesions and leg health.
Correspondingly, the broilers showed their highest amount of walking at 17 light hours — 4% of the time compared to less than 1% at 23 hours.
The turkeys, who were studied at 14 and 17 weeks, also showed the least activity at 23 hours of light, when they rested up to 73% of the time (at 17 weeks), while in 14 hours of light they rested for 67% of the time. Their walking achieved a high of 5% of their time (at 17 weeks) in 14 light hours with a low of 3% at 23 hours.
Because both birds exhibited the most activity around 17 hours of light, Schwean-Lardner stated that this photoperiod “should be probably the bottom end of our lighting program for both bird strains,” and 23 hours of light should not be used in commercial houses for either strain.
The study also examined time spent at feeders. It has been assumed that giving birds longer light access would lead to them spending more time at feeders and increasing their feed intake. The study found the opposite so that longer light resulted in a decrease in the percentage of time spent at feeders by both birds.
For example, under 23 hours of light, the percent of time broilers spent at feeders decreased from 7% to 4%, resulting in lower bodyweight. Turkeys experienced a similar result as their market bodyweights were highest at 14 hours of light and lowest at 23 hours.
Other behaviors affected by light
The study also examined comfort and exploratory behaviors, such as preening, which often indicate positive welfare for the birds. The effect of photoperiod on broilers was dramatic. When reared under 23 hours of light, broilers spent only 1% of their time preening, but that percentage increased as the amount of light decreased. This “decline is much faster and much more severe with broilers” than turkeys, Schwean-Lardner noted, and so the broilers really have trouble with those long day lengths.
The turkeys also displayed behavioral changes related to light, though not as severe as those in broilers. For example, exploratory pecking — a positive indicator of welfare — was lowest when turkeys were reared under 23 hours of light and highest under 14 hours. Schwean-Lardner noted that turkeys are also prone to aggressive pecking so that “species-specific research into managing abnormal behavior” is needed.
Overall, Schwean-Lardner concluded that the study findings showed that “we should not be using broiler data to make our decisions for turkeys.” She also reemphasized the need for more research to be done specifically on turkeys.
