Effects of hatching time and hatching system on broiler chick development

 Key words: hatching time, hatching system, chick physiology, broiler growth, chick quality.

Chicks hatch over a time window of 24-36 hours and are only removed from the hatcher when the majority of the chicks have hatched. Especially for the early hatching chicks this leads to delays in the first feed and water access and consequently negative effects on chick development. In an alternative hatching system, named Patio, the hatching and brooding phase are combined, thereby enabling direct posthatch feed and water access. Environmental conditions in Patio differ from those in hatchers, which may further influence chick quality, physiology, and growth. Chicks hatching at different moments may respond differently to these different conditions in both hatching systems. In this thesis, the first aim was to determine effects of hatching in the Patio system on hatchability, chick quality, and growth. The second aim was to determine the physiological status of chicks of different hatching moments, in the hatcher and the Patio system, at hatch, and at chick collection (21.5 d of incubation). Effects of hatching time and moment of first feed and water access on posthatch growth were also included.  

Hatchability of fertile eggs was 1.03% higher in the Patio system compared to the hatcher, which was probably due to different climate conditions  during the hatching phase. At hatching, chick physiology was not clearly affected by hatching system, but effects of moment of hatching in the hatch window were clear: longer incubation times led to increased organ weights and decreased yolk weights, suggesting a higher level of maturation in late hatching chicks. At the moment of chick collection, Patio chicks, having immediate feed and water access,showed larger body and organ weights, higher hepatic glycogen reserves, higher plasma glucose and T₃ levels, and lower corticosterone levels compared to hatcher chicks which were fasted between hatching and chick collection. Usinga chick qualitative score based on physical traits and the incidence of second grade chicks, chick quality was lower in Patio than in hatcher chicks. However the quality scores used were not predictive for posthatch performance. Patio chicks showed improved posthatch growth compared to hatcher chicks, which was not related to different climate conditions during hatching, but to earlier feed and water access. Apart from higher growth from d0-7 in early and midterm vs late hatching chicks, effects of hatching time on growth were not clear from this thesis.

In conclusion, despite considerable differences in climate and other environmental factors, effects of hatching system on physiology of broiler chickens at hatch and growth performance up to slaughter age are limited. Perinatal chick physiology is affected by the moment of hatching in the hatch window, and by posthatch conditions in the hatching system, especially early feed and water access.