Little is known about physiological responses of early- versus late-hatching chicks
to early posthatch conditions in broiler practice. We investigated effects of hatching
time on perinatal broiler physiology in 2 hatching systems, differing in conditions:
a conventional hatcher, where chicks are deprived of feed and water between hatching
and the moment of chick pulling (d E21.5), and a patio system, in which the hatching
and brooding phase are combined, and chicks have immediate posthatch feed and water
access. Climate conditions in patio also differ with about 3°C lower temperature and
20% lower RH compared with conventional hatchers. At E18, fertile eggs were transferred
to either a hatcher or the patio until the end of incubation. From each system, 50
newly hatched chicks were collected at 3 hatching times: at 468 h (early), 483 h (midterm),
and 498 h (late) of incubation, of which 25 chicks were decapitated for analyses of
physiological parameters. The other 25 chicks were returned to the hatching system
for analyses after 515 h of incubation (E21.5). At hatch, weights of the heart, lungs,
stomach, and intestine increased with hatching time, concurrent with a decrease in
residual yolk weight, regardless of hatching system, and indicating that later hatching
chicks are more matured. Weights of the heart, liver, stomach, and intestines were
lower in hatcher than in patio chicks. Between hatch and E21.5, residual yolk weight
decreased, whereas organ weights increased in both fasted hatcher and fed patio chicks,
but at a higher rate in the latter. At E21.5, plasma glucose and triiodothyronine
had increased with time after hatch in patio chicks, whereas levels were similar among
hatching times and lower in hatcher chicks. Early feed and water access seems to enable
early hatching chicks to compensate for their apparent disadvantage in development
at hatching, whereas chicks subjected to fasting show metabolic adaptations to preserve
nutrients. Chick physiology at chick pulling time was shown to vary with time after
hatching and posthatch conditions, especially feed access.