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Weise, Heinrich (2008): Lichtbedingten Einflüsse auf Verhalten und Leistung in der Hähnchenmast: Eine Feldstudie unter Berücksichtigung tierschutzrechtlicher und wirtschaftlicher Aspekte. Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

A field study on lighting in the production of meat-type-chickens was conducted between April 2006 and February 2007. Part 1 comprised a survey on lighting practices in a substantial number of broiler farms in southern Germany (n = 187 broiler stables covering a total area of 276.337 m²). It was carried out on the basis of a questionnaire adapted to broiler management. The focus of data collection was put on animal welfare issues of lighting. It was found that in conventional broiler farming closed buildings, with or without windows, are the most common kind of facility used. This applies to the number of farms as well as to the total area. A comparatively high proportion of stables from the early days of poultry farming in Germany shows that these agricultural buildings often remain in use unchanged for decades. Thus, once taken, decisions on lighting have practical consequences over the whole life-cycle of an agricultural building. The surroundings in closed stables are primarily conceived to accommodate the need of farm staff for work-efficiency and workplace-safety. Scientific findings on visual perception of poultry have not been implemented systematically in poultry farming, yet even though lighting constitutes a central management factor which can influence behaviour and health of the animals to a substantial degree. An exception is the fact that conventional fluorescent lights with a flicker frequency of 100 Hz, which poultry may perceive as discontinuous, have largely been eliminated from the farms we examined. Subsequently the lighting environments of characteristic types of broiler sheds were examined by means of spectrophotometry. Data were collected on illuminance, irradiance, UVA-irradiance and colour temperature in summer as well as in winter. Substantial differences were found between the two sampling dates, particularly where ultraviolet radiation was concerned. Additionally considerable differences between the type of building (with or without daylight) could be described. Taking into consideration the enlarged sensory facilities of birds (perception of ultraviolet radiation, flicker fusion frequency higher than 100 Hz), it can be concluded that the currently used methods for sampling light intensity, particularly the lux-unit, are suitable for poultry to a limited extent only. Part 2 was a study on the effects of two lighting programmes which differed exclusively in intensity (5 lx and 20 lx) from the 13th day of the fattening period. The following parameters were collected and evaluated under field conditions: ► Development of intraocular pressure ► Development of eye measures ► Behaviour and time-budget ► Excretion of glucocorticoids (corticosterone) ► Performance parameters Under 5 lx a modulation of intraocular pressure was observed. Moreover all eye measures were larger under 5 lx than under 20 lx. A biological relevance of these differences, which were very slight, can be denied with a high certainty. The animals kept under 20 lx showed phases of higher activity and more explorative and comfort behaviour than the group raised under 5 lx. These results could be interpreted as a decrease in global activity due to the low light intensity. The lighting programme with an intensity of 5 lx resulted in a tendency for a higher excretion of fecal corticosterone, which was significant on day 35 only. This could be interpreted as a direct influence of dark surroundings on glucocorticoid metabolism. Bright lighting (20 lx) increased the risk for necrotic dermatitis (inflammatory process) by a factor of more than three. A prolonged fattening time of 37-39 days predisposed the animals to the development of necrotic dermatitis as well. Pododermatitis score was better under dim lighting. Further effects of lighting on production parameters could not be found. Taken together, these results give strong hints that a decrease of light intensity to approximately 5 lx at the beginning of the third week of a production cycle may constitute a tool to improve performance and prevent skin damage. Nonetheless these low light intensities could be stressful for the animals. These results were collected under field conditions and under certain restrictions. More research under controlled conditions remains therefore to be done.