soon get used to when the off-time is approaching and will ‘crop-up’ and drink prior to the lights being turned off. Any lighting programme adjustments should only be made to the on-time. In terms of light intensity during this period it has been shown that brighter light promotes activity and chicks prefer the brighter light. “We recommend a minimum intensity of 25 lux in the darkest part of the brooding area as measured at chick height,” says Brendan Graaf. “The intensity also needs to be as uniform across this area as possible in order to maintain good flock uniformity. Light intensity at floor level should not vary by more than 20% from the brightest to the darkest are- as in the barn. Chicks tend to migrate towards the brightest areas and if intensity varies by more than 20%, the chicks will not be evenly and uniformly distributed within the house”.
Benefit of darkness It was once believed that subjecting broilers to a continuous or near continuous light period for the life of the flock would maximise their growth performance. However, broilers reared under an adequate period of darkness often have better growth rates, lower feed conversion, fewer skeletal defects and improved immune function compared to birds reared under continuous light conditions. “After chicks reach 130- 180g or 7 days of age, we recommend introducing a single 6-hour block of darkness by adjusting the on-time of the lights. The off-time must remain the same as set on day 1 and this change should be done as a single change and not grad- ually. During the same period you can begin to gradually
(over 5-7 days) to reduce the light intensity to 5-10 lux for the remainder of the grow period, unless local legislation prohib- its this reduction. An EU directive, for example, requires a minimum of 20 lux throughout the cycle,” Graaf explains. The 6-hour dark period should be continued until the final week before processing. Nearing the final days of production, five days prior to processing, reduce the dark period by one hour per day (subject to local legislation) to allow for addi- tional gains. This also helps to reduce flightiness during catching if this is performed during the day – as is often the case. This practice works especially well in hot climate coun- tries since it has been shown birds are more heat-stressed during the dark period, therefore reducing the dark period will result in birds that are less heat-stressed during the final few days. In terms of wavelength/colour of light used there is some evi- dence that broilers reared under shorter wavelength light (green and blue) showed improved performance compared to using traditional white lights. The use of poultry-specific LED lighting has been shown to have a benefit on broiler per- formance, as well as a long-term financial benefit for the pro- ducer. “There are many aspects to lighting programmes and there are many different lighting programmes which can be implemented with great success”, Graaf concludes. “You can always optimise your lighting programme based on your op- erations and local conditions, while observing local regula- tions. An optimum programme will promote the full genetic potential and health of your flock, not to mention excellent welfare outcomes”.
▶ POULTRY WORLD | No. 5, 2020
Uniform light in- tensity across the broiler house during brooding can promote feed and water in- take, as well as promote health and welfare.
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