The effect of dark brooders on feather pecking on commercial farms

Commercial laying hen chicks experience continuous light for up to 24 h/day in the first
week of life. Under these conditions, active chicks disturb, and may direct feather pecks
towards resting ones. Previous experimental work with small groups showed that both
problems were reduced in chicks brooded by dark brooders (heaters). The current study
aimed to extend these small-scale trials by examining the use of dark brooders on two com-
mercial rearing farms. Each farm contributed two identical houses, one of them equipped
with dark brooders and the other with regular brooders. The experiment comprised five
replicates, each consisting of one dark brooder flock and one control flock (total of 10
flocks). Each flock contained 2000 Columbian Blacktail chicks with intact beaks, which
were reared to organic standards. Observations took place three times during the rearing
period at 1, 8 and 16 weeks and three of the five replicates were also followed into lay,
with observations at 25 and 35 weeks. Bird weights, the evenness of body weight, mor-
tality at the end of rear, feather pecking, the percentage of the flock with missing feathers
and individual feather scores were measured, as well as the flock’s reaction to a novel
object and an approaching human in selected areas of the house. Apart from mortality,
which was analysed as a paired t-test in PASW Statistics 18, data were ordered in three (or
four) levels (visits within (flock within) replicate within farm) and were analysed using the
multilevel statistical software MLwiN 2.25. Treatment and age were entered in the model
as explanatory variables. On average, across observations taken at all ages, dark brooder
flocks performed significantly less severe feather pecking than control flocks ( 2 = 12.215,
df = 1, P = 0.0005) and had a significantly lower percentage of birds with missing feathers
( 2 = 7.380, df = 1, P = 0.007). Individual feather condition deteriorated faster in the control
treatment (treatment × age2 : 2 = 12.148, df = 1, P = 0.0005). There was also an interaction
between treatment × age for weight ( 2 = 11.087, df = 1, P = 0.0009) which meant that dark
brooded birds ended up slightly heavier than birds from the control treatment. Mortality
at the end of rear, gentle feather pecking and evenness of the weight were not measurably
affected by treatment. The novel object and human approach test gave mixed results. In
conclusion we found no detrimental effects of dark brooding on commercial farms and sug-
gest this is a promising approach to reducing problems with feather pecking and generally
improving the welfare of commercial pullets.