Dear Aggie

Question and Answer for February 17:

What does a bear hibernating, a cow producing milk, a chicken, and a person who has seasonal affective disorder all have in common in the wintertime?

No, this isn’t a riddle. All of these mammals are having a physiological response to the shorter periods of sunlight during the day. Decreased amounts of natural daylight (short photoperiod) impact all mammals, as there is lower production of serotonin and in turn melatonin in the pineal gland. In animals, melatonin is involved in the synchronization of the circadian rhythms including sleep-wake timing, blood pressure regulation, seasonal reproduction, and many other functions. Day length, and thus knowledge of the season of the year, is vital to many animals. A number of biological and behavioral changes are dependent on this knowledge. Together with temperature changes, photoperiod (length of daylight) provokes changes in the color of fur and feathers, migration, entry into hibernation, sexual behavior, and even the resizing of sexual organs. For the bear, these hormone changes signal that it’s time to hibernate. For many humans, we get sluggish, more tired and for some, we have to deal with seasonal affective disorder (SAD). The reduced level of sunlight in fall and winter may cause winter-onset SAD. This decrease in sunlight can disrupt your body's internal clock and lead to feelings of depression, because of the drop in serotonin production. The sleep patterns are in-turn impacted by changes in melatonin.

So what about the cow and the chicken?

The cow and chicken are exposed to the same natural light as the bear and the human and have the same hormonal changes. However, their reactions are a little different. The hormone changes due to natural lighting don’t end with serotonin and melatonin. There are other hormones that change including prolactin and IgF1. In chickens, these hormone changes lead to a decrease (or even an end) to egg production. In cattle, this leads to a decreased appetite and decreased milk production.

So what can we do to keep the chicken laying eggs and the cow milking in the winter? The answer is simple – provide more natural light. If we can provide 16 hours of daylight and 8 hours of dark to both chickens and cows, we can help maintain production levels, whether that be eggs or milk. As more hours of light are provided, less melatonin is produced and more IgF1 is produced. However, providing more than 16 hours of light can be detrimental. The balance of 16:8 is key to maximize production. Many dairy farms have lights that run on timers to provide the cows 16 hours of light and 8 hours of darkness. For dairy cows, the production difference between a long photoperiod (16 hours of light) and a short photoperiod can be up to 10%.

In summary, photoperiod management offers a cost effective solution to producers of all sizes and a novel tool to improve the efficiency of milk and egg production in the winter months.

By Kim Morrill, Regional Dairy Specialist, Northern New York Regional Ag Team


Catherine Moore
Agriculture, Natural Resources & Fort Drum Issue Leader
(315) 788-8450 ext. 236

Last updated February 17, 2018