Management of lighting programs for improved performance of broiler chickens
Proper lighting programs for broiler chickens
Lighting program and adjusting it (light- dark hours and how light is distributed during the day) has a significant effect on welfare, performance, and productivity of the broiler chickens .Devising a defined pattern for lighting and darkness leads to regular periods of rest and activity. On the other hand, many of the physiological and behavioral processes of birds follow natural daily rhythm. Therefore, regulating a proper lighting program has a significant effect on behavioral patterns and growth of birds.
The applied lighting program must be simple and at the same time applicable. A suitable lighting program depends on environmental conditions, market requirements, and the time of loading the flocks. However, some managerial points have to be observed under any circumstances and then different adjustments are conducted depending on the flock’s conditions.
Four important components of a lighting program are:
• Duration of light cycle: the number of light-dark hours that is implemented during a 24-hours period
• Lighting period distribution: how the light-dark hours are distributed during a 24-hours period.
• Wavelength: light color
• Light intensity: how much this light illuminates
The interacting effects of these factors have to be taken into account as well. For instance, some production or welfare parameters in poultry (such as growth rate, conversion ratio, and mortality) may vary as the light- dark distribution, lighting intensity, and wavelength vary.
Gradual changes in lighting program
A sudden change in light/dark time incurs a rapid drop in feed consumption, body weight, and feed efficiency. Although broiler chickens acclimate their behavioral responses in response to light variations (changing the feed consumption pattern), making a change in lighting program (the length of lighting period and light intensity) is more plausible. The nutritional activities of broiler chickens immediately after the beginning of lighting and approximately one hour before darkness is at its highest level. Using a gradual program of starting light/dark program (during a 15-45 minutes span) leads to gradual movement of poultry birds toward the feeder and can stop the crowd. As the lighting program changes, it is better to make gradual changes during 2-3 days rather than a sudden and rapid change.
A suitable lighting program should be: simple and practical
Continuous or semi-continuous lighting programs are not desirable; long and continuous dark periods may put the provision of blood supply to the growth plate at risk.
Intermittent exposure to darkness accelerates the growth rate, improves conversion ratio, enhances immune system responses from the poultry against the diseases and eventually decreases the losses. The secretion of melatonin during the darkness leads to a rise in the release of calcitonin and Parathyroid hormone, a rise in calcium transfer and useful variations in the activity of osteoblasts and osteoclasts which result in better growth of bones.
Figure. Method of implementing lighting program with continuous darkness 1
Offering a proper lighting program depends on many factors. But, observing the following points can be effective in biological performance and welfare of the poultry:
Day 1-7: chickens must get 23 hours light and 1 hour darkness.
Day 7-28: dark hours gradually and intermittently reach to 6 hours a day.
After day 28: dark hours gradually and intermittently reach to 4 hours a day; this gradual reduction turns the dark hours to 1 hour at day 42.
From day 42 until slaughter: one hour of darkness a day.
Comparing different wavelengths of monochrome light with similar intensity, it seems that chickens exposed to wavelength of 415-560 nanometer (blue to green) have better growth rate compared with the group that have been exposed to waves higher than 635 nanometer (red) or a widespread range (white). This means that better growth firstly depends on wavelengths rather than light intensity in that increasing light intensity typically reduces growth.
It is suggested that the growth response to wavelength is dependent on age, so that the green light would induce a faster initial growth and blue light leads to higher weight gain after week two and can improve feed conversion ratio.
From day 1-7, the light intensity of 30-40 lux (3-4 foot candle) and after that at least 5-10 lux (0.5-1 foot candle) leads to improved nutrition activities and growth.
Low light intensity (lower than 0.5 foot candle and 0.5 lux) may have negative effects on the performance of poultry, including:
- Increase in losses, worsening of FCR, and reduction in body growth
- Reduction in eyesight
- Increase in leg abnormalities
- Reduction in activity and welfare of poultry
- Affecting the physiological rhythm of poultries (they may not distinguish between day and night).
To examine the effectiveness of the light of the poultry house, regular tests must be conducted. One solution is to stand at the center of the poultry house and turn off the lights, thereby you can identify any source of light leaks to the poultry house.
The light intensity must be uniformly distributed throughout the poultry house (placing a reflecting mirror above the lamp can improve the light distribution). Lux meter is a cheap but significant device which indicates whether or not the light is at an appropriate level.