Do Chicks Benefit From 24 Hours of Light?

George Entz Thanks for your feedback

George Entz How old are condemns with longer than four hours dark

Dr. Mike Czarick, Please email me at entzgeorge20@gmail.com. Thanks.

Dr. Mike Czarick If the dark period exceeds 4 hours the birds are getting very excited at light on and crowd in front of the feeders. This bears the risk of deep scratches on the back. Splitting the dark periods in two phases may be better in this respect. Werner

Werner Bessei This is why I believe it is important to use a "dawn/dusk" dimmer. If the lights are brought on gradually you will avoid potential piling and scratching problems. In my opinion breaking a six hour dark period into two three dark periods somewhat defeats the purpose of having a dark period. I know I would rather sleep six hours continuously than have two three hour naps.

Werner Bessei but than they are not getting 4 hours rest which is very important for growth performance

Dr. Mike Czarick so would I agree

Dr. Mike Czarick, Your dusk/dawn time, is 30 minutes sufficient in 2-5 lux barns?

Dr. Mike Czarick it depends what you intend to achieve. If the objective is to alllow the development of a cicadian rhythm 4 hours are sufficient. The objective to provide 6 or 8 hours continuous rest may not be accepted by all birds. It has been shown that feed intake of broilers increases during long dark periods. This may not be the case if the birds have enough time to increase feed intake before dusk. A diiming period indeed helps to anticipate the dark period. But the development of the crop capacity may require more time, especially in young birds. Werner

Werner Bessei And that is why we are conducting research trials looking at 6 hrs of darkness. We have a long way to go but it does look like that birds don't need 24 hours of light during brooding. What is the optimal dark period? Hard to say.

Werner Bessei, What about when having 8 hours of darkness, have 1 hour of light for birds to eat in the middle of the dark period, same as is done within the Layer industry. Layers don't precieve the hour of light as a change of Day/Night as long as the light period does not go over 1 hour if I remember correctly. Has anyone tried that in Broilers?

George Entz One argument I could make against a very long dark period is that it would likely increase bird heat stress during warm weather. The shorter the day, the more calories the birds have to taken in during the shorter day, the greater the amount of heat the birds will produce during the shorter day (more Btu's/hr)

Dr. Mike Czarick that is correct. In this case you need a light phase period during the night. But it must not cover the whole night. Werner

George EntzHere is another talk from Dr. Schwean-Lardner where they found that increasing dar hours shifts the time of gaining weight to later (after 32 days) in their lives. https://www.wattagnet.com/articles/41944-why-broilers-need-darkness-everyday?v=preview

Dan Hofer, I have opened birds before lights came on at 6 hours of darkness and there was still feed present in the GIT so that confirmed to me Dr. Karen's work, that birds regulate the feed passage time according to hours of darkness, is correct. They were checked after they had been on 6 hours of darkness for a week, so It is quite possible that when first using 6 hours that the GIT runs empty till they are " programmed" to it. I don't have a reference (don't remember the paper) but I have read that it can be overcome by doing it gradually. I myself would never recommend changing hours of darkness more then 1/2 hour a day. I haven't seen differences in cellulitis from 4 to 6 hours. I have tried the light stimulation you mentioned and I found that in heat stress moments that "maybe" it works. Maybe Dr. Mike can comment if he has tried that technique to released trapped hot air in high density barns. But the rest of the time all I have seen is the birds eat more in the 20 minute time frame and less during. But because you increase lights they become more active and all birds want to eat at the same time, which caused more competition at the feeders, especially in the late stages, and that caused a increase in cellulitis for me. Maybe the difference in our results is feeder space/bird, diet type and density, bird density, lux starting point and increase used, and time between stimulation.