Thermal Manipulation During the Embryonic Stage and the Post-Hatch Characteristics of Broiler Chickens

The objective of this study was to evaluate the influence of thermal manipulation during incubation on the hatchability, the performance, the carcass characteristics, the intestinal villi, the nutrient metabolizability, and some physiological parameters in broiler chickens. Ross eggs were randomly distributed into four commercial automatic incubators. The treatments were as follows: incubator kept at 37.5 °C throughout the incubation period (Ctrl-control), and incubator temperature increased to 39 °C on days 16, 17, and 18 of incubation for 3 (T_3h), 12 (T_12h), or 24 h (T_24h). The chicks were housed in an experimental performance barn and kept until 42 days of age under standard rearing conditions. The hatchability was lower when T_24h was used. During the time after hatching, T_3h caused higher levels of heat shock protein 70 (HSP70) in the liver, a faster breathing rate, and a drop in the cloacal temperature and hematocrit. T_12h increased the respiratory rate. T_24h decreased the hematocrit, the weight gain, and the feed intake. The thermal manipulation during incubation did not affect the carcass characteristics, intestinal villi, or metabolizability of nutrients. It was concluded that raising the incubator temperature for 3 h during late incubation may be beneficial for thermoregulation, but raising it for 24 h during this period impairs animal performance.