Real-time variations in body temperature of laying hens with increasing ambient temperature at different relative humidity levels

Abstract

In order to measure the real-time variations in body temperature with increasing ambient temperature (AT) at different relative humidity (RH) levels, 60 Jinghong laying hens (35-wk-old) were raised in 3 controlled climate chambers (10 cages with 2 birds per chamber). The RH was fixed at one of 3 levels comprising 35, 50, or 85%, and the AT was increased gradually by 1 degree per 0.5 h from 18 to 35°C in the 3 chambers. The core temperature (CT) and surface temperature (ST) of the hens, as well as the AT in the 3 chambers were recorded at 3 min intervals using mini temperature data loggers. The data were analyzed with a broken-line model to determine the inflection point temperature (IPT, the certain AT above which the body temperature of the hens started to change). The experiment was repeated 3 times on 3 d. The IPTs of the laying hens were 23.89 and 25.46°C based on ST and CT at 50% RH, respectively, which indicated that the upper critical temperature of the thermoneutral zone of hens may be a specific temperature between 23.89°C and 25.46°C. The IPTs of the laying hens were 24.11 and 25.20°C based on ST and CT at RH 35%, respectively, and 21.93 and 24.45°C at RH 85%. The RH significantly affected the IPT of ST (P < 0.001). The IPTs were higher at 35 and 50% RH than that at 85% RH (P < 0.05). The coefficients of variation for the IPTs between individual hens were 2.96 to 4.51, and coefficients of variation for the IPTs for the same bird measured on 3 d were 0.69 to 1.59, thereby indicating that this method for estimating the IPTs of hens is stable and repeatable, although more samples are needed. In conclusion, our results indicate that analyzing the real-time variation in body temperature with increasing AT is a reliable method for estimating the IPT to provide an important reference for regulating the temperature in poultry houses.

Effects of heat stress on pullet cloacal and body temperature

“…The thermal comfort ( TC ) zone for homeothermic animals is characterized by a range of environmental temperatures, within which animals have minimal and nearly constant energy expenditure for maintaining body temperature ( BT ) ( Curtis, 1983 , Chang et al., 2018 ). Body temperature for poultry normally varies from 41°C to 42°C ( Wilson, 1948 , Welker et al., 2008 ), and to maintain BT in this range, the thermoregulatory system adjusts physiological responses to increase or decrease body heat loss ( Sturkie, 1986 , Sahin et al., 2009 , Taylor et al., 2014 ).…”

“…Body temperature for poultry normally varies from 41°C to 42°C ( Wilson, 1948 , Welker et al., 2008 ), and to maintain BT in this range, the thermoregulatory system adjusts physiological responses to increase or decrease body heat loss ( Sturkie, 1986 , Sahin et al., 2009 , Taylor et al., 2014 ). Outside of the TC zone in situations characterized by heat stress ( HS ) or cold stress, birds further adjust their metabolism to further compensate their energy balance ( Nascimento et al., 2013 , Hester et al., 2015 , Arcila et al., 2018 , Chang et al., 2018 ).…”

“…Especially in large-scale production systems, in which maximum efficiency of production is sought, it is important to minimize exposure to HS. For this, it is necessary to use methods for adjusting the environmental temperature based on bird's requirements ( Edgar et al., 2013 , Abreu et al., 2017 , Chang et al., 2018 ).…”

“…Measuring BT is a method to assess the severity of HS ( Unruh et al., 2017 , Chang et al., 2018 ). The standard tool for BT measurement is the cloacal thermometer; however, this method is invasive, requires handling the birds, can be stressful, and can yield altered or misleading results ( Eddy et al., 2001 , Edgar et al., 2013 , McManus et al., 2016 , Vicente-Pérez et al., 2016 , Andrade et al., 2017 ).…”

Comparative study of adaptation in three chicken genotypes under humid tropical conditions of Nigeria

“…However, as the upper critical limit is approached, they shift to EHL method (panting), characterized by various heat stress responses. A relatively low relative humidity is preferred to high one under such condition of high environmental temperature (Aksit, Yalcin, Ozkan, Metin, & Ozdemir, 2006;Chang et al., 2018). High environmental temperature that usually exceeds the thermal comfort of the birds, coupled with raised relative humidity, increases the heat load and limits efficiency of evaporative heat loss (Ebeid, Suzuki, & Sugiyama, 2012;Sinha, Kamboj, Ranjan, & Lathwal, 2017).…”