Fig 1.
A) Average eggshell temperature from day 13 to hatching in the LT (36°C), CK (37.5°C) and HT (39°C) treatments. B) Mean differences between eggshell and incubator air temperature from day 13 to 21 of incubation in the LT (36°C), CK (37.5°C) and HT (39°C) treatments. *Indicates a difference between means (P < 0.05); reported values represent the means ± SD (n = 10 eggs/treatment).
Table 1.
Body surface and rectal temperatures of hatchlings obtained from eggs exposed to low temperature (LT; 36°C), control temperature (CK, 37.5°C) or high temperature (HT, 39°C) treatments from day 13 to 21 of incubation (means ± SD).
Table 2.
Feathering characteristics of hatchlings obtained from eggs exposed to low (LT, 36°C), control (CK, 37.5°C) or high (HT, 39°C) temperature treatments from day 13 to 21 of incubation (means ± SD).
Table 3.
Skin, epidermis and dermis thickness (μm) and blood vessel number (counts per field) and perimeter (μm) of chicks obtained from eggs exposed to low (LT, 36°C), control (CK, 37.5°C) or high (HT, 39°C) temperature treatments from day 13 to 21 of incubation (means ± SD).
Fig 2.
Skin histological sections of broiler hatchlings submitted to low (LT, 36°C, A and D), control (CK, 37.5°C, B and E) or heat (HT, 39°C, C and F) incubation treatments during fetal development.
A-C) Neck skin thickness was lower in the heat (C) than in cold and control treatments (A and B, respectively). D-F) Blood vessels perimeter increased with incubation temperature. e: epidermis. d: dermis. Black arrows indicate cross sections of blood vessels. Red double arrows indicate skin thickness.
Fig 3.
Plasma concentrations of triiodothyronine (T3, ng/ml), thyroxine (T4, ng/ml), T3/T4 ratio and growth hormone (GH, ng/ml) of hatchlings obtained from eggs exposed to low (LT, 36°C), control (CK, 37.5°C) or high (HT, 39°C) temperature treatments from day 13 to 21 of incubation.
* Indicates a difference between means (P < 0.05); values represent the means ± SD (n = 24 chicks/treatment).
Fig 4.
Preferred ambient temperature of hatchlings submitted to low (LT, 36°C), control (CK, 37.5°C) or high (HT,39°C) temperature treatments from day 13 to 21 of incubation.
* Indicates a difference between means (P < 0.05); values represent the means ± SD (n = 16 chicks/treatment).