| There are increasing complaint from domestic consumers about the quality and flavor of poultry product and various international trade bans to Chinese poultry meat, this study focused on the main cause of these problems, and aimed to look at methodology of monitoring indices for heat stress alarm system of broilers, in order to provide comfort environment for animals, consequently poultry meat quality was improved.The summer conditions of Guangzhou, Wuhan and Ha'erbin were simulated to investigate the circadian rhythms of blood thyroid iodohormones and Creatine Kinase (CK) of 58-d old Arbor Acres (AA) broilers within 5 days exposure, in order to determine sampling time of sensitive indices for heat stress alarm system of broilers. The blood samples were taken 6 times per day from different individuals at AMO:00, AM4:00, AM8:00, AM12:00, PM4:00 and PM8:00 respectively. The results revealed that both triiodothyronine (T3) and thyroxine (T4) had two peaks, which showed at AM12:00 and PM12:00, AM8:00 and PM12:00 respectively, the lowest concentration of both T3 and T4 appeared at PM4:00, therefore appropriate blood sample should be taken according to the rhythms. There were sexual differences in CK circadian rhythms of broilers under simulated summer conditions, the CK circadian of female chickens followed the diurnal change of environmental temperature, but the shape of CK circadian rhythm of male broilers had reverse trend, lagging 8 hours. The reaction of male and female broiler to heat stress were also different, therefore male and female broilers should be considered separately in trials. T3 was a sensitive heat-stress indicator of broilers, T4 can be considered as reference, T3/T4 ratio is not suitable to be heat stress index of broilers.Physiological indices, including rectal temperature (RT), surface temperature (ST), and mean body temperature (MBT), serum thyroid hormone (thiiodothyronine, T3 and thyroxine T4), creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations of 42-d old Arbor Acres (AA) broilers were determined after 120 min exposure to 18 acute thermal conditions formed by 3 2 3 factorial combinations ofdry-bulb temperature (tdb) of 35 C, 38 C, and 41 C; dew-point temperature (tap) of 19.4 C and 26.1 C; and air velocity (V) of 0, 0.7, and 1.2 m s"1. The results showed that both RT and TS were sensitive heat-stress indices of broilers, and temperature-humidity index (THI) of 6-week old broiler was developed based on RT, THI = 0.81 x/rfj>+o.l9 xtwt> where tdb = dry-bulb temperature, twb= wet-bulb temperature. LDH and CK were affected various experimental factors, both were not good indicators of broiler heat-stress.Core body temperature (tb) of market-size male broilers (46 ? d; 2.8 ?.1 kg; Ross x Ross breed) was continuously measured by telemetry during acute, 90- to 240-min exposures to 18 thermally challenging conditions. The thermal conditions consisted of 18 factorial combinations of three dry-bulb air temperatures (tdb; 35 C, 38 C, and 41 C), two dewpoint temperatures (tdp; 19.4 C and 26.1 C), and three air velocities (V; 0.2, 0.7, and 1.2 m s"1). Based on tb rise after 90-min exposures to the thermal conditions, a temperature-humidity-velocity index (THVI) was developed to delineate the synergistic effects of the thermal components on the birds, having the form of THVI = (0.85tdb + 0.15twb) x v '058, where twb = wet-bulb temperature. The homeostasis state of the bird was classified as normal, alert, danger, or emergency, which correspond to a tb rise threshold of 1.0 C, 2.5 C, 4.0 C, or >4.0 C, respectively. These different homeostasis states were functionally and graphically expressed in terms of THVI and exposure time. A practice of environmental evaluation for broiler operations was suggested according to both THVI and heat exposing time.Surface wetting cooling 46-d old Ross x Ross male and 42-d old Arbor Acres (AA) broiler chickens was investigated under 18 acute thermal conditions formed by 3 x 2 x 3 factorial combinations of dry-bulb temperature (tdb) of 35 C, 38...
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