Little is known about physiological responses of early- versus late-hatching chicks to early post-hatch conditions in broiler practice, according to Lotte van der Ven of Vencomatic in the Netherlands and co-authors there and at the Catholic University of Leuven in Belgium and Wageningen University in the Netherlands.

In a paper published in Poultry Science, they report their investigation into the effects of hatching time on perinatal broiler physiology in two hatching systems, differing in conditions: a conventional hatcher, where chicks are deprived of feed and water between hatching and the moment of chick pulling (day E21.5), and a patio system, in which the hatching and brooding phase are combined, and chicks have immediate access to feed and water post-hatch. Climate conditions in patio also differ with about 3°C lower temperature and 20 per cent lower relative humidity than conventional hatchers.

On day 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 three hatching times: at 468 hours (early), 483 hours (mid-term) and 498 hours (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 hours of incubation (day 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 mature.

Weights of the heart, liver, stomach, and intestines were lower in hatcher than in patio chicks.

Between hatch and day 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.

On day 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, concluded van der Ven and her co-authors. They added that chick physiology at chick pulling time was shown to vary with time after hatching and post-hatch conditions, especially feed access.

Reference

^{van de Ven L.J.F., A.V. van Wagenberg, E. Decuypere, B. Kemp and H. van den Brand. 2013. Perinatal broiler physiology between hatching and chick collection in 2 hatching systems. Poult. Sci. 92(4):1050-1061. doi: 10.3382/ps.2012-02534}

May 2013