Effect of sex on hatch time and correlation between hatch time and post-hatch weight and pododermatitis: a preliminary experiment

Previous research has reported that incubation duration and hatch time are affected by pre-incubation and incubation conditions and by the sex of embryos. the aim of this experiment was: (1) to correlate embryo sex, egg weight and chick weight with hatch time; and (2) to study the effect of hatch time on the post-hatch body weight and pododermatitis up to slaughter age. A total of 19,200 eggs from same ROSS 308 breeder flock (aged 40 weeks) were incubated in two standard incubators (Petersime n.v.) with a capacity of 9600 eggs each. Twenty eggs (focal eggs) were randomly selected per incubator. At transfer (Day18 of incubation), focal eggs were separated by mesh dividers. The hatch time of the focal chicks was labelled using video records taken by two analogue cameras placed 30 cm above the baskets. Of 40 focal eggs, 36 hatched and these focal chicks were marked with a non-toxic coloured spray. At takeoff, each focal chick was weighed and sexed by a feather sexing expert. Focal chicks were divided into 4 pens (9 focal chicks per pen: 2 of males and 2 of females) with other chicks. The total number of chicks per pen was 241 males and 272 females in order to have a final density of 39 kg/m² at slaughter age. During the rearing period, the focal chicks were individually weighed at Day21 and Day28. Focal chicks were scored for pododermatitis at Day21 and Day28 according to the method developed by Michel et al. (2012) where scores range from 1 (no lesion) to 5 (severe lesion).