I consulted with Dr. Mike Petrik, DVM, MSc, a laying hen veterinarian whose only job is to care for chickens about this subject. Dr. Petrik has more than 13 years of practice behind his medical education and training, including a Master of Science in animal welfare. I asked Dr. Petrik the following questions to debunk often-spouted misinformation about supplemental light in the hen house:
1) Does supplemental lighting harm a hen or shorten a hen’s lifespan? (short answer=NO)
2) Will supplemental lighting cause a hen to run out of eggs prematurely? (short answer=NO)
The following was his reply:
“Seasonal lighting is one of the most important factors in a laying hen’s life. The increasing day length in the spring stimulates the hormone cascade that gets her body prepared for, and instigates egg production. The decreasing day-length in the fall will cause hens to go “on strike”….put their ovaries back into dormancy, and free-load for the winter. In temperate climates, where hens evolved (mostly Indo-China, India and some in the Mediterranean), this was a good strategy for decreasing nutrient needs during the winter, when food and other resources were scarce.
Day length is not actually registered by the eyes of the chicken. The pineal gland in the brains of chickens sits just beneath a thin area of the skull, right between the hen’s eyes. This organ is what senses day length, and stimulates the pituitary gland to start hormone production that results in eggs being laid. In experiments at the University of Guelph in Canada, researchers used genetically blind chickens (a line of birds that have a genetic defect that results in no retina, and therefore no sight) to study the effect of different kinds of light and day length on sexual maturity in hens. This was the most elegant way to ensure that nothing the bird was seeing was affecting sexual maturity…..these hens had identical responses to increased day length as their normally sighted counterparts!
Hens don’t actually sense day length, they perceive the length of the dark period. The longest dark time is the thing that defines day-length to hens. It is possible (and common in professional egg farms) to give flocks naps during the day….if the dark time for the nap is shorter than the night time, the hen does not respond to it, other than to settle down and rest for a couple hours [meaning, they will still lay eggs in the morning].
The important points are this: if you want you chickens to keep laying eggs during the fall and winter months, you need to keep the length of their “day” longer than 13 or 14 hours. The hens can stay in production at less hours of light than this, but not if they are exposed to the long days we have in the summer (ie: if they are kept in a barn all the time). To do this, the simplest way to do this is to look up a sunset/sunrise chart for your latitude, see what the earliest sunset time is, then set an automatic timer in your coop to come on 15 hours previous to that. Do this in the summer, when the sun rises before your lights come on.
If you have already had hens come out of lay, due to the fall, you can stimulate them back into lay by setting your timer for 20 minutes before dawn, then turning it 20 minutes earlier every week until 15 hours of day length is reached. Your hens should come back into production within 4-6 weeks of this stimulation (it takes that long for the hormone cascade to result in egg production).
I’ve heard people comment that artificial light will decrease the hen’s lifespan, or decrease the number of eggs she lays during her lifetime. There is no evidence of supplemental lighting decreasing longevity, provided you supply adequate nutrition and allow the birds to molt every 12-18 months. The molt is necessary to replenish bone stores, rebuild feather strength and let the hens gain some muscle and fat stores. Otherwise, the hen is perfectly capable of healthily laying eggs throughout the year.
As for her “lifetime” supply of eggs, she is born with the number of possible ova (yolks) already set. These number in the hundreds of thousands and would take decades of daily egg production to deplete. A hen will stop laying because of old age (and therefore produce less eggs in her life) long before she would ever run out of ova to produce eggs.