Lichtbedingten Einflüsse auf Verhalten und Leistung in der Hähnchenmast

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.