I think in a word ‘Yes’ I personally believe that the Darkness System is a ‘Stressor’ as is a Race, hard training, illness, moult, lack of sustenance etc. A pigeon can cope with ‘Stressors’ if they are kept within limits but if they are excessive then the pigeons immune system will begin to fail and the pigeon will become ill.
Having got the above out of the way then obviously I would favour reducing the amount of time a pigeon is subject to the Darkness System to minimum that is effective.
If your young birds are born in January you do not need to put them on the Darkness System immediately in fact if your racing season ends in August there is littler benefit in using the system at all for these early bred young birds.
The second and third rounds of youngsters are different they should be put on the system immediately they are weaned.
To clarify, maybe the procedure should be called the Lightness System as you are controlling the hours of Lightness per day to 10 hours
The hours are not specific so you can, within reason adjust the hours to suit your own work hours, it does not have to be 6pm in the morning, 8pm or even later can be just as effective.
The Darkness System does not have to extend through the season if your Race Season ends in August the beginning of June is a good time to come off the system.
Obviously if you want to enter long races later in the Year then you should extend the Darkness System until the end of June.
I have few pet theories regarding the Darkness System that I will pen again
1) As mentioned above I think the Darkness System adds to a racing pigeons stress so reduce this by having lights with dimmer switches so that when the blinds are brought down the light dims over say 15 minutes so pigeons can go to rest naturally.
2) As the blinds are introduced they can sometimes restrict the flow of fresh air in your loft, so I think the use of some quiet ventilation fans on timers would be a good investment. These can be switched on for a few minutes every hour during the darkness period, and when you are cleaning out the loft. This will protect your and the pigeons health.
3) To reduce the shock at the beginning of June (1st week) extend the hours of Lightness by 1/2 hour per day for a week before completely removing the blinds. Aim to get the pigeons familiar to the natural time for sunrise as possible. If one had timers on the blinds then if your normal darkness hours were say from 6pm to 8am then
Day 1 – would be from 6pm to 7:30
Day 2 – would be from 6pm to 7:00
Day 3 – would be from 6pm to 6:30
Day 4 – would be from 6pm to 6:00
Day 5 – would be from 5:30 to 6:00
Day 6 – would be from 5:00 to 6:00
Day 7 – There would be no blinds and natural light hours
4) As the birds at this time are subject to a lot of stress provide Vitamin B in the feed at least once per week.