Stocking density within chick transport boxes: effects on leghorn chick stress and box microclimate

Recommendations for the optimal stocking density (SD) of chicks within transport boxes have not previously been published, with current recommendations lacking scientific support. As a result of concerns from welfare organizations regarding high SD in delivery boxes, a field trial was conducted at a commercial hatchery to understand SD effects on chick stress and box microclimate. Lohmann LSL-Lite chicks (n = 3,630) were placed in plastic transport boxes (58 × 46 cm) for a 7-h simulated transport period (uncontrolled humidity; 27°C). The SD treatments (trt) used were 80, 100, or 120 chicks/box (33.4, 26.7, or 22.2 cm²/chick). Group body weight (BW); vent temperature; concentrations of corticosterone, electrolytes, and glucose; and yolk sac weights were measured pre- and post-trt. Temperature and relative humidity (RH) were recorded every 5 min in the boxes. Thermal images of the boxes were taken every h for box floor and chick surface temperature and to calculate spatial area used per chick. Body weight, vent temperature, yolk sac weights, and corticosterone concentration did not differ between SD trt post-trt. Box temperature and RH increased with increasing SD. Thermal images showed the minimum temperature was lowest, and temperature variability was greatest, in the 80 trt compared to the 100 and 120 trts. The spatial area used per chick differed between trt and chicks occupied less than the total spatial area available in all trt. In conclusion, within the conditions used in this study, altering SD did not affect bird wellbeing, but reducing the density increased temperature variability within the boxes.