Effects of stress during commercial hatching on growth, egg production and feather pecking in laying hens.

Every year, billions of egg layer chicks around the world are hatched under highly stressful, industrial circumstances. Here, it is investigated how the stressful procedure in the commercial hatchery, including incubation, hatching, processing, and transport affects the chicks with regards to traits relevant for the egg production industry. These traits were compared to those of a control group hatched in a small incubator and handled gently och quietly in a quiet room without any processing and transport. The chicks were weighed at hatch and at eight additional time points: 4 days, 1 week (w), 2 w, 3 w, 5 w, 8 w, 20 w and 25 w of age. Feather pecking was studied at 15 w of age and damages to the feathers and injuries on the comb and wattle were assessed at 25 w of age. From 19 w of age, eggs were collected on three days per week, counted and weighed. Chicks from a commercial hatchery had a lower hatch weight than control chicks (p<0.001). At 20 w of age, the weight of the commercial hatched chicks was still numerically lower, although this did not reach statistical significance. Commercially hatched chicks tended to show more feather pecking behaviour at 15 w of age compared to control chicks (p<0.1), although feather condition at 25 w of age showed the opposite pattern. Regarding production, commercially hatched chickens laid fewer (p<0.05) and smaller (p<0.05) eggs than chicks hatched and handled under calm circumstances. From this experiment, it is concluded that the stressful experience in the commercial hatchery has an overall negative effect on traits relevant for the industry.