Abstract
This study aimed to investigate effects of eggshell temperature (EST) during early and late incubation on embryo and hatchling development of broiler chicks. A total of 720 eggs were randomly allocated to 3 treatment groups: control EST (37.8°C during the first 14 d and 36.8°C between d 15 and 21 of incubation), early high EST (as control, but 38.9(∘)C between d 4 and 7), and late high EST treatment (37.8°C during the first 14 d and 38.2°C between d 15 and 21). At d 18 of incubation, the length of the femur, tibia, and metatarsus were found to be lower in the early high EST treatment than in both other treatment. Hatchability was higher in the early high and control EST treatment than in the late high EST treatment (Δ = 4.2% on average; P = 0.02), whereas the opposite was found for late term embryonic mortality (Δ = 4.0% on average; P = 0.02). Navel score was higher for the late high EST treatment than for the early high EST and control treatment (1.36 vs. 1.19 and 1.17, respectively; P < 0.001). At hatch, chick weight, and organ weights were lower in the late high EST treatment than in the control treatment, with the early high EST treatment in between. At hatch, most femur, tibia, and metatarsus characteristics were lower for the early high EST treatment compared to both other treatments. The same was found for tibia ash, Ca, and P concentrations. Blood ALP and P levels were higher in the control group than in both other treatment groups. It can be concluded that early high EST particularly affected bone development during incubation, whereas late high EST particularly resulted in a decline in hatchability and chick quality in broiler chicks.