Effect of constant or weekly varied eggshell temperature during incubation on broiler performance up until slaughter age

During incubation, embryo development is particularly influenced by temperature. Thevast majority of commercial hatcheries aim at a constant eggshell temperature (EST) of37.8°C throughout incubation. However, it has been shown recently that lowering EST(36.7°C) in the last week of incubation might improve embryo development, as higher(yolk-free) body mass and relative organ weights at hatch were found. In addition,raising EST slightly in phases during which oxygen is not limited yet (before the lastweek of incubation), might improve embryo development as well. It is hypothesizedthat a lower EST (36.7°) in the last week of incubation and a higher EST (38.9°C) in thesecond week of incubation improve embryo development and perinatal chick qualitycompared to a constant intermediate EST (37.6°) throughout incubation. Moreover,EST during incubation might have long term effects on broiler performance as theincubation period covers a substantial part of their whole lifespan and as it is knownfor many animal species that perinatal experiences have an impact in later life. Totest this hypothesis, Ross 308 eggs from a prime parent flock were incubated in a 2x2experimental design. All eggs were incubated at a normal (37.8°C) EST until embryonicday (E) 7. Thereafter, eggs were either incubated at a normal (37.8°C) or high (38.9°C)EST during the second week (E7 – E14) of incubation and a normal (37.8°C) or low(36.7°C) EST during the last week (E14 – E21) of incubation. Within 6 hours afterhatch, chick development was evaluated by chick weight, length, navelscore, and organweights. Posthatch, 5 males and 5 females were housed in a 2 m2 pen with 8 replicatesper treatment (n=320) and reared until slaughter age (D42). Growth and feed intakewere monitored weekly. At D28, D35, and D39 gait was scored from all animals. Atslaughter, foot-pad dermatitis, hock burns, and carcass characteristics were determined.Preliminary results indicate that a low EST from E15 onwards results in slower growthand on average 103 g. lower body weight at slaughter. Other parameters were notsignificantly different or not analysed yet (e.g. carcass characteristics) at the moment ofabstract submission.