Production Data
The production company supplied the following information:
total mortality (% of flock dead before slaughter); total culls (% total
mortality from culling); daily mortality and culls (recorded on
a daily basis by the farm manager); growth rate (average daily bird
growth weight calculated from daily recording with automatic
weighers in each house and additional weekly weighing by hand);
hockburn (% of birds with any permanent discoloration to the
hocks, assessed at the slaughter plant post mortem and after
cleaning and defeathering); pododermatitis (% of birds with any
lesion to the foot pad, assessed at the slaughter plant post mortem
and after cleaning and defeathering). In addition, the company
supplied information on gas consumption per house, water
consumption per house, age at which the birds were sold, total
weight sold and the farm manager’s recordings of relative humidity
(rH) measured with a hand-held rH meter. Company data were
validated as far as possible; for example, the totals of the mortality
and cull data as they were recorded on the daily house sheets were
checked against the final flock mortality and culls as given by the
company and the company provided data before being told optical
flow results for that flock. Systematic bias in the collection of post
mortem data was controlled for by collecting data from the
slaughterhouse ‘blind’ (i.e. the staff assessing hockburn and pododermatitis
at the slaughter plant operated to standard company
procedures and did not know which flocks they were assessing).