Temperature during the last week of incubation. II. Effects on first week broiler development and performance.

Little is known about applying various eggshell temperatures (EST) during the last week of incubation. In particular, the effect of an EST below 37.8°C during the last week of incubation is poorly investigated. Therefore, we investigated effects of EST of 35.6, 36.7, 37.8, or 38.9°C applied from d of incubation (E) 15, E17, or E19 on first week broiler development and performance. A total of 2,850 first grade eggs of a 43 wk old Ross 308 broiler breeder flock were incubated at an EST of 37.8°C until E15. From E15, E17, or E19 onward, eggs were incubated at an EST of 35.6, 36.7, 37.8, or 38.9°C. Chick quality was determined at placement in the broiler house and organ development was measured at d 7. BW was determined at placement, d4, and d7. Feed intake (FI) was measured at d4 and d7 and G:F was calculated between placement and d4, and between d4 and d7. Chick quality at placement was higher at an EST of 35.6°C compared to all other EST treatments, expressed by a longer chick length and highest prevalence of closed navels. BW d 7 was higher at an EST of 36.7°C compared to all other EST treatments, which was not caused by a higher FI during the first week. A higher G:F between d 0 and d 7 was found at an EST of 36.7°C compared to 35.6 and 38.9°C. At d 7, a higher relative heart weight was found at an EST of 35.6 compared to 38.9°C. This study indicates that an EST of 38.9°C applied from E15 onward negatively affected chick quality, organ development, and G:F until d 7 compared to 37.8°C. Moreover, an EST of 36.7°C had a clear positive effect on chick quality, organ development, G:F, and growth performance until d 7. An EST of 35.6°C resulted in equal or higher chick quality and organ weights compared to 36.7°C, but this was not reflected in performance parameters.