Manipulação térmica durante a incubação de ovos como medida para amenizar o estresse por calor em frangos de corte

Abstract

Heat stress is one of the main problems faced in broiler production. Due to this, it is necessary to develop strategies that make chickens more tolerant to environmental temperature variations. Therefore, the objective was to evaluate the influence of thermal manipulation during incubation on hatch parameters, and post-hatch evaluations of productive performance, carcass characteristics, intestinal villi, nutrient metabolizability and immunological, biochemical and behavioral parameters of broilers. On the 15th day of incubation, 864 fertile eggs of the Ross® strain from a commercial hatchery were randomly assigned to four commercial automatic incubators. The treatments were: Ctrl - control, eggs kept at 37.5°C throughout the incubation period; T3h - Increase in temperature to 39°C for 3 hours on days 16, 17 and 18 of incubation; T12h - Increase in temperature to 39°C for 12 hours on days 16, 17 and 18 of incubation; and T24h - Increase in temperature to 39°C for 24 hours on days 16, 17 and 18 of incubation. After hatching, the birds were housed in the experimental shed and kept until 42 days of age. Increasing the temperature for 24 hours on days 16, 17 and 18 of incubation reduced (P<0.05) weight gain and feed intake at 42 days of age. At 24 days, lower cloacal temperature was observed (P<0.05) in birds from eggs incubated with an increase in temperature for 3 hours and a higher respiratory rate at 31 days was observed (P<0.05) when the temperature was increased for 3 or 12 hours. At 42 days, lower hematocrit was observed (P<0.05) when the incubation temperature was increased for 3 or 24 hours and higher gene expression of Hsp70 in the liver (P<0.05) when the temperature was increased for 3 hours. For the other parameters, no difference was observed between the experimental treatments. It is concluded that thermal manipulation during incubation can influence the performance and physiological characteristics related to the thermotolerance of birds. Increasing the incubation temperature to 39°C for 3 hours on days 16, 17 and 18 of incubation can be beneficial to the thermotolerance of the birds, and this temperature increase maintained for 24 hours impairs the post-hatch performance of the broilers.