Effects of high CO₂ level during early incubation and late incubation in ovo dexamethasone injection on perinatal embryonic parameters and post-hatch growth of broilers

Abstract

1. A total of 1200 Cobb broiler breeder eggs were incubated under either standard conditions (C group) or high CO₂ levels (CO₂ group) during the first 10 d of incubation. The CO₂ level of the CO₂ incubator was attained gradually by a natural build-up of CO₂ due to air-tight closure of the incubator. From d 10 of incubation onwards, all eggs were incubated under standard incubation conditions. At d 18 of incubation, the eggs of both incubation groups (CO₂ and C group) were either injected with water-soluble dexamethasone (DEXA group) or with saline (0·9% NaCl; saline group) or were not injected (control).

2. Body weights, plasma hormonal concentrations (T₃, T₄ and corticosteroid) and glucose concentrations were measured regularly during the perinatal (at IP, internal pipping) and post-hatch period (at 1, 2, 4 and 6 weeks post-hatch). Additionally, hatchability and pattern of embryonic mortality were determined after hatch.

3. The results showed that high CO₂ levels during the first 10 d of incubation or dexamethasone injection at d 18 of incubation decreased embryo mortality, mainly because of a reduction in embryo malpositioning. However, a combination of a CO₂ incubation and a dexamethasone injection led to an increase in embryo mortality and therefore a decrease in hatchability.

4. Although dexamethasone injection at embryonic d 18 decreased body weight in the second week of the rearing period and CO₂ incubation increased body weight during the first 2 weeks of the rearing period, no consistent effect of both the incubation and injection treatments on body weight at slaughter age was observed.

Acknowledgements

K. Tona was granted a postdoctoral fellow from KU Leuven during this study. V. Bruggeman has a postdoctoral FWO grant from the Fund for Scientific Research, Flanders, Belgium. This work was supported by the Fund for Scientific Research, Flanders (FWO, Vlaanderen) Belgium (Grant No. G0286.04).