Introducing his presentation at IPSF this year, Dr Roger Lien explained that he an his colleagues at Auburn University have carried out a series of broiler lighting trials, looking at different photoperiods and light intensities.

For the work he reported, they opted to compare the current US National Chicken Council (NCC) Broiler Guidelines with those of the European Union (EU).

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Dr Lien explained that the NCC guidelines require at least four hours of darkness although shorter dark periods are allowed in the first week and the last two weeks. There is no requirement regarding intensity but when continuous or near-continuous lighting is used, it should be at a subdued level. A dim intensity is common in the US, and light traps are rare. The Food Marketing Institute/National Council of Chain Restaurants (FMI/NCCR) recommends providing less darkness only in the first week and the last.

The guidelines in the EU are more explicit and are evolving, as Dr Lien explained. In 2002, at least two hours of darkness were required, and lighting should be one foot-candle (FC; 1 FC = 10.76 lux) in the first week and 2 FC thereafter. In 2005, it was proposed that the birds should have at least 8 hours of darkness during a 24-hour period, including one period of 4 hours (less during the first and last three days). The minimum intensity was 2 FC. The guideline proposed in 2007 required at least 6 hours of darkness, including at least one period of four hours darkness (less during the first 7 and last 3 days). The minimum intensity throughout was set at 2 FC.

Previous work at Auburn included five trials comparing different photoperiods and light intensities. From this and work reported by Classen, Dr Lien highlighted three generalities: broiler growth was slower with less than 20 hours of light per day; growth may have been improved by dim light levels (less than 0.25 FC), and breast meat and carcass yield were reduced by decreased photoperiod or intensity.

Latest Experiment

A total of 960 male Ross 708 chicks were used in the latest experiment at Auburn, and 12 light- and environment-controlled rooms, explained Dr Lien.

There were three lighting treatments:

Key differences were that the light intensities for the 'US' treatment (NCC) were lower than the other two treatments. The 14 B treatment gave the birds the opportunity for what Dr Lien described as a 'midnight snack' – a two-hour feeding break between two periods of darkness and inactivity.

The researchers observed some significant differences between the lighting treatments. (Difference were regarded as significant with P<0.05 for body weight, feed intake and feed conversion, and P<0.1 for uniformity, mortality and processing parameters).

Dr Lien identified four main findings from his latest work. Firstly, splitting the dark period (16 B versus 14 B) increased body weight and feed consumption. The 16 B birds had similar body weights to the NCC treatment, indicating the birds had indeed taken advantage of the extra light and taken a 'midnight snack'. Second, the 20 D birds were more uniform than those on the 16 B treatment. Third, early mortality was higher with the 20 D treatment. The cause(s) of death and relationship with dim lighting are unclear. Finally, the 14 B treatment gave decreased yields of the wing and drum, and a slight numerical increase in breast yield.

To a question from the audience, Dr Lien said he had not observed leg problems with any of the treatments.

Implications for New EU Broiler Welfare Guidelines

The guidelines on broiler welfare in the European Union have been subject to frequent revision, reflecting growing consumer concerns for animal welfare in general, and as research provides answers to some of the fundamental questions of bird well-being and behaviour.

The Department for the Environment, Food and Rural Affairs (Defra) in the UK currently has a document entitled Code of Recommendations for the Welfare of Livestock: Meat Chickens and Breeding Chickens, inviting comments on the latest proposals for broiler welfare by 12 April. The proposals will apply only to England.

In this Code, the welfare of meat chickens and breeding chickens is considered within a framework, elaborated by the Farm Animal Welfare Council and known as the 'Five Freedoms': freedom from hunger and thirst; freedom from discomfort; freedom from pain, injury or disease; freedom to express normal behaviour and freedom from fear and distress.

Applied to lighting, the birds need sufficient light in order to move around to find feed and water, express normal behaviour and exercise, as well as to be properly observed. The birds also need the opportunity to rest undisturbed, which is more easily achieved during a period of darkness. A period of darkness is also necessary in order to acclimatise the birds in case of a power or lighting failure.

According to the Defra Code, Schedule 1 of the Welfare of Farmed Animals (England) Regulations 2007 (as amended) applied to all meat chickens. It states that animals kept in buildings must not be kept in permanent darkness. Where the natural light available in a building is insufficient to meet the physiological or ethological needs of any animals being kept in it, appropriate artificial lighting must be provided. Animals kept in buildings must not be kept without an appropriate period of rest from artificial lighting.

For conventionally reared meat chickens, i.e. commercial indoor broilers, the Code refers to Schedule 10 of the Welfare of Farmed Animals (England) Regulations 2007 (as amended). It states that all buildings must have lighting with an intensity of at least 20 lux during the lighting period, measured at bird eye level and illuminating at least 80 per cent of the usable area. A temporary reduction in the lighting level may be allowed when necessary following veterinary advice. Within seven days from the time when the chickens are placed in the building and until three days before the expected time of slaughter, the lighting must follow a 24-hour rhythm and include periods of darkness lasting at least six hours in total, with at least one uninterrupted period of darkness of at least four hours, excluding dimming periods.

The results from the experiment conducted by Dr Lien and colleagues at Auburn University do not appear to contradict the Defra Code for commercial indoor-reared broilers. The light intensity of 20 lux (approximately 2 FC) reduced mortality in the Auburn trial compared to the dim light of the NCC treatment (0.1 to 0.5 FC). The new element of splitting the total dark period allows the birds an additional opportunity to feed, thus avoiding excessive hunger while still allowing for sufficient rest.

Reference

Lien, R.J., J.B. Hess and S.F. Bilgili. 2009. Effects of American and proposed European lighting programs on broiler live and processing performance. Proc. International Poultry Scientific Forum, 26-27 January 2009. Atlanta, Georgia.

Further Reading

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Go to our previous news item on the publication of the proposed changes to the EU rules on broiler welfare by clicking here.