Effect OF Daily Increasing Temperature On Thermoregulation Of Laying Hens

Temperature-reducing establishments, such as fans and cooling pads, were generally installed in large-scale hen houses. Through opening the fans and cooling pads, the thermal environment in hen houses could be regulated within a certain range. However, there was little scientific basis for opening the fans and cooling pads to regulate the thermal environment. Improper adjustment was not only directly influenced the growth and healthy of laying hens, but also caused the energy wasting and breeding costs rising.Poultry are a homeothermic, and can maintain thermostasis by regulating the heat production and loss, so the thermoregulation is a significant index for reflecting the poultry comfort degree. This article was aimed to analyze the effects of daily increasing temperature in different relative humidity（RH）on poultry thermoregulation indicators such as fasted heat production（FHP）, surface temperature（ST）and core temperature（CT）. Through Broken-line analysis, we get the inflection point temperature（IPt）of thermoregulation indicators. For this reason, the thermal environment was divided,and provided the reference for establishing the comfort environment model and regulating the thermal environment scientifically.1 Effects of Oviposition and Feeding Behavior on Core and Skin Temperature of Laying HensTwelve Jing Hong hens aged 34 weeks were assigned to six cages, one cage included two birds and were kept at environmental control chambers（ambient temperature: 20℃, relative humidity: 60%）. All hens were exposed to 16L:8D up to the end of experiment and fed twice a day. Miniature temperature data loggers measured the core and skin temperature, and the data was recorded every 3 minutes, which lasted 48 h. The time of oviposition and feeding were recorded by digital infrared video camera. The results that analyzed by repeated measurement showed as follows: 1) Oviposition had an effect on the core temperature（P<0.01） and the skin temperature（P=0.082）. Thereinto, the core temperature of egg-laying period was 0.24 ℃ higher than that of pre-laying（P<0.01） and 0.37 ℃ higher than that of post-laying（P<0.01）. Compared with the pre-laying period, the skin temperature of egg-laying period had a tendency to increase（0.05<P<0.1）..2) Feeding had a significant effect on the core（P=0.01） and skin temperature（P=0.006）. Compared with the core and skin temperature of the 1 h before feeding, the core and skin temperature of the 1² h after feeding increased 0.12 ℃（P<0.05） and 0.35 ℃（P<0.05,respectively; 2 h after feeding, the core and skin temperature were back to normal. 3） During the day（ 11:00¹2:00 、 15:00¹6:00 、 19:00²0:00）, the core and skin temperature had no differences（P>0.05）,which significantly higher than that at night（P<0.01）.In conclusion, the oviposition and feeding behavior significantly improved the core and skin temperature. Therefore, evaluating the comfortable level in the basis of body temperature in laying hens, the interference of oviposition and feeding should be avoided.2 Effects of daily increasing temperature（different RH） on thermoregulation of laying hensEighty Jing Hong hens aged 34 weeks were assigned to 4 environmental control houses, and one cage included two birds. AT and RH setting as follows: Ⅰ: 20°C,60%RH.Ⅱ: The temperature and RH was set at 18°C,30% at 11:00. Every half an hour, the temperature was increased by 1°C from 18°C to35°C.After laying hens stayed in 35°C half an hour, the AT and RH turned to 20°C,60%RH.Ⅲ During the experiment, the RH was set at 60%.Ⅳ: During the experiment, the RH was set at 90%.The other operations of Ⅲ and Ⅳwere the same as Ⅱ.The experiment lasted for 3 days. The results showed that :1) Daily increasing temperature had no significant difference of CT and ST between days 1 and 3（P>0.05）. 2)Daily increasing temperature had a significant influence on CT,ST and percentage of feeding behaviors（P<0.01）. Due to the large variation in different time of laying hens, the datas of the percentage of lying behavior, water intake and FHP of 2 days were averaged to proceeding the Broken-line analysis, not variance analysis. 3) Through the Broken-line analysis, the IPt of ST was23°C, CT was 25.2°C, percentage of feeding behaviors was 28.2°C, FHP was 28.0°C in 60%RH.On the basis of the result, the comfort zone was the temperature below 23°C,which the laying hens did not regulate the heat production and loss to maintain the constant body temperature; The normal region was the 23-25.2°C which the laying hens could regulate the heat loss to maintain the constant body temperature. The safe region was 25-28.2°C and the warning zone was over 28.2°C, which the laying hens were in the obvious state of heat stress. 4) The IPt of CT, ST and percentage of feeding behaviors were moved forward in high humidity（90%）, which indicated the high humidity could decreased the heat resistance.5) In the temperature region of 22-35°C, the THI model of ST was THI=0.84Tdb+0.16 T_wb, while the THI model of CT was THI=0.83Tdb+0.17T_wb(dry-bulb temperature:Tdb;wet-dry-bulb temperature: T_wb)3 Broken-line analysis of ST and CT and identification of the THI modelFour different hen houses were selected and were recorded the AT and relative humidity for 24 h,every 3min. Twelve Jing Hong hens which were healthy and had similar weight were selected to record CT and ST for 2 days. The results showed that the trend of CT and ST were similar to the trend of ambient temperature, due to the lower weight value of T_wb InTHI model and the small variation of RH in hen houses. The trend of CT and ST were similar to the trend of ambient temperature, but ST and CT were increased in the region of turning on the lights, feedig and oviposition, while ST and CT were decreased in the region of turning off the lights. The regression equations of ambient temperature and CT and ST in 4 hen houses were similar to regression equations in the environment control house,indicating that the regression formula was reliable in the third chapter which could be used as an important basis for regulating AT in the henhouse.