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Heat stress is an increasing challenge for production animals, particularly in warmer regions of the world. The aim of this study was to compare the fit of three different relationships when modelling respiration rate (RR) and rectal temperature (RT) in animals exposed to increased load. Data from three published studies on finishing pigs, gestating sows and dairy cows were analysed. RR and RT are characterized by being unaffected by increased heat load as long as it is kept below a certain level, and in warmer conditions they increase with increased heat load. As an expression of heat load either the air temperature or the ET (Effective Temperature) was used. The ET unites the effect of air temperature, air humidity and velocity on the animal perception of increased heat load. The relationship between RR and RT and the temperature or the ET was analysed by multiple change point regression and the cubic relationships were modelled. In general, the models provided better fits for RR compared to RT. Relationships with an unaffected piece followed by a quadratic relationship and the cubic relationships performed nearly equally well. Using ET resulted in better correlations than using temperature alone for gestating sows and dairy cows. • Effective Temperature with air velocity gave better correlations than temperature. • The quadratic broken line and the cubic relationships performed nearly equally well. • The models provided better fits for respiration rate compared to rectal temperature. [ABSTRACT FROM AUTHOR]

Abstract Broiler chickens are selected to undergo a rapid six-week hatch-to-slaughter growth phase to attain large body and muscle mass. Broilers have relatively high resting and locomotor metabolic costs suggesting that adaptive thermoregulatory mechanisms are required to dissipate excess heat. Using thermal imaging in the growing broiler we characterised the trajectory of radiative and convective cooling in still air across broiler development. Scaling of head, tarsus and toe surface area did not deviate from body mass2/3 while torso area increased with positive allometry, body mass0.82, reflecting increased feather coverage and/or disproportionate abdominal/thoracic growth. Despite relatively increased area, the body became less effective for heat transfer presumably due to increasing feather coverage. Conversely, the magnitude of heat exchange from the distal hindlimbs was improved in larger birds. Overall capacity to transfer heat by convection and radiation in still air was attenuated over development, since the proportion of resting metabolic rate accounted for decreased in standing and sitting postures. This physiological constraint could be ameliorated by increased latent heat transfer or provision of environmental ventilation, which we modelled according to industrial guidelines. Based on models, higher airspeeds coincided with improved convective cooling that assisted in maintaining the proportion of RMR accounted for by convective and radiative heat transfer. These data highlight the potentially adverse thermoregulatory effects of rapid growth rate and body mass increases, which may contribute to the increased sedentary resting and decreased locomotor behaviour observed in large broilers. Highlights • Broiler chickens develop very rapidly to reach high slaughter weights. • Convective and radiative heat transfer become less effective over development. • Modelled airflow improved the contribution of sensible heat loss. • Constraints on heat loss may contribute to reduced locomotor behaviour. [ABSTRACT FROM AUTHOR]

The wet bulb globe temperature (WBGT) is an effective measure for risk screening to prevent heat dISOrders. However, a heat risk evaluation by WBGT requires adjustments depending on the clothing. In this study, we proposed a new effective WBGT (WBGT eff * ) for general vapor permeable clothing ensembles and vapor impermeable protective clothing that is applicable to occupants engaged in moderate intensity work with a metabolic heat production value of around 174 W/m 2 . WBGT eff * enables the conversion of heat stress into the scale experienced by the occupant dressed in the basic clothing ensemble (work clothes) based on the heat balances for a human body. We confirmed that WBGT eff * was effective for expressing the critical thermal environments for the prescriptive zones for occupants wearing vapor impermeable protective clothing. Based on WBGT eff * , we succeeded in clarifying how the weights for natural wet bulb, globe, and air temperatures and the intercept changed depending on clothing properties and the surrounding environmental factors when heat stress is expressed by the weighted sum of natural wet bulb, globe, and air temperatures and the intercept. The weight of environmental temperatures (globe and air temperatures) for WBGT eff * for vapor impermeable protective clothing increased compared with that for general vapor permeable clothing, whereas that of the natural wet bulb temperature decreased. For WBGT eff * in outdoor conditions with a solar load, the weighting ratio of globe temperature increased and that of air temperature decreased with air velocity. Approximation equations of WBGT eff * were proposed for both general vapor permeable clothing ensembles and for vapor impermeable protective clothing. [ABSTRACT FROM AUTHOR]

Global warming combined with increased production (i.e. more piglets, more milk and consequently more heat) means that sows are more often challenged by heat stress. The objective was to develop an effective temperature (ET) equation to predict how air temperature, velocity and humidity affect the respiration rate (RR), rectal temperature (RT) and skin temperature (ST) as an expression of heat stress in gestating sows in order to elucidate the relationship between the thermal parameters and the sows' perception of the environment. The experimental room was equipped with a negative pressure ventilation system with diffuse air inlet through the ceiling, electrical heaters, steam generators and dehumidifiers. An air distribution unit was constructed to generate vertical air velocity. A total of 16 gestating sows were exposed to three temperatures (25°C, 29°C and 33°C), two levels of relative humidity (30% and 70%) and three levels of air velocity (0.2 ms−1, 1 ms−1 and 2.5 ms−1). The RR, RT and ST were recorded every 30 min throughout the three 2-h test periods. The estimated effects of humidity and velocity in relation to effect of temperature was nearly independent of whether it was determined from RR or RT, whereas the effect of humidity was much smaller when determined from ST. High coefficients of determination (>0.97) were found for the second order relationship between the estimated ET and RR, RT and ST. An increase in relative humidity from 50 to 70% corresponded to an increase in ET of 0.9°C, while an increase in air velocity from 0.2 to 1.0 ms−1 corresponded to a decrease in ET of 1.2°C. The applied ET equation was useful for expressing the combined effect of temperature, humidity and velocity on animals exposed to heat stress. However, multiplying the effect of velocity by the temperature gradient between the animal and the surrounding air did not improve the estimation. • The Effective Temperature (ET) equation expressed the united effect of air temperature, humidity and velocity. • Respiration rate (RR) and rectal temperature (RT) estimated the ET nearly equally well. • When ET was determined from skin temperature (ST), the effect of humidity was much smaller. • R2 > 0.97 for the second order relationship between ET and RR, RT and ST. [ABSTRACT FROM AUTHOR]

A multi-fan system (MFS) for single culture beds was developed to improve the airflow in a plant factory with artificial light. The MFS had seven fans which were installed on both the front and back sides of culture beds to generate airflow from two opposite horizontal directions. The fans that push the air into the culture bed were air inlets while those that pull the air out of the culture bed were air outlets. In this study, three airflow patterns were evaluated: T 1 , the front and back sides of the culture bed were air inlets; T 2 , the front side was an air inlet and the backside was an air outlet; and T 3 , both the front and back sides were air outlets. A culture bed with no MFS was used as a control (T 4). Lettuce growth and tipburn occurrence were evaluated and leaf boundary layer resistance (1/ g bv), sensible heat flux (S h), and latent heat flux (L h) of lettuce plants were estimated. The airflow pattern in T 1 improved the air velocity (V a) by an average of 0.75 m s-1 and a variation coefficient of 65%. The 1/ g bv decreased significantly with the increase in V a , and the lowest value of 54.0 s m-1 was observed in T 1. The low resistance to heat and moisture transfer enhanced the S h and L h of lettuce plants. The average S h and L h were 40% and 46% higher in T 1 compared with those in T 4. The fresh and dry weights of lettuce plants in T 1 were 1.13 and 1.06 higher than those in T 4 , respectively. No tipburn occurrence was observed in lettuce plants grown under the MFS while five leaves per plant were injured with tipburn in T 4. The results indicated that improving the airflow can improve the growth of indoor cultured lettuce and alleviate the occurrence of tipburn due to the decrease in the 1/ g bv and the increase in the transpiration rate. • Leaf boundary layer resistance decreased by 45% with increasing air velocity from 0.23 to 0.75 m s-1. • Sensible and latent heat flux increased 40 and 46% with increasing air velocity from 0.23 and 0.75 m s−1. • Under a light intensity of 200 μmol m-2 s-1, leaf temperature was always lower than air temperature. • Increasing air velocity enhanced the transpiration rate, therefore, lettuce tipburn suppressed. [ABSTRACT FROM AUTHOR]