| The aim of this research is to determine the effects of summer climate in southwest China characterized by hot-humid environment on feeding behavior of growing-finishing pigs and physiological and biochemical parameters of sows. The present research ascertained the change regulations of growing-finishing pigs feeding behavior and pregnant sows physiological and biochemical parameters in hot-humid environment in order to help producers and researchers to adjust rearing process according to the regulations under hot-humid environment and manage the herd of growing- finishing pigs more efficiently, and to provide theoretical basis for sows production and environmental warning.Taking the summer hot-humid environment in Chongqing as the experimental conditions on behalf of the climate in southwest region of China. The temperature, humidity, air velocity and growing-finishing pigs feeding behavior were monitored in 24-hour real-time by remote weather monitoring systems and performance measurement system. Skin temperature and respiration rate of pregnant sows under different environment parameter were measured as well. Blood was collected under the setting temperature, of which the biochemical indices were analyzed by Elisa assay. The results were shown that:(1) The environmental analysis of pig houses of whole experimental period shows that the highest temperature, average daily and daily average relative humidity of performance measurement and natural ventilation houses in summer were 35℃,30℃,80% respectively, the hot-humid days were up to 30. There was a highly significant negative correlation between temperature and humidity (P<0.01, r=-0.54, r=-0.88). In the pad-fan house, the highest temperature, average daily temperature and average daily relative humidity were 32℃,26.5℃,92% respectively, and there was no significant correlation between temperature and humidity.(2) The feeding behavior showed a circadian rhythm under hot-humid and non-hot-humid conditions. The feed intake, feed frequency and feed time between 6:00-9:00 am and 15:00-19:00 pm was significantly higher than other periods within a day and more than 52% of the feeding behavior occurred in this period. The feeding behavior of growing-finishing pigs was significantly affected by temperature, humidity and their interaction (P<0.05). The increase in temperature, humidity and THI highly significantly decreased feed intake per kilogram of body weight and feeding time (P<0.01).(3) The skin temperature and respiration rate of pregnant sows were affected by temperature, air velocity and THI, but the humidity had no significant on these parameters in pad-fan house (P<0.05). Overall, the skin temperature and respiration rate increased highly significantly as THI and temperature increased while the skin temperature and respiration rate decreased as air velocity increased (P<0.01). There was significant interaction between temperature and humidity, temperature and air velocity, THI and air velocity as they influenced skin temperature. In natural ventilation house, the pregnant sow’s skin temperature respiration rate were affected significant by temperature and THI, the interaction between temperature and humidity was not significant (P>0.05).(4) The temperature, air velocity and their interaction significantly affected serum CORT concentration of sows (P<0.05). The concentration of MDA and HSP70 were significantly affected by environment parameters. When the temperature was out of the TNZ, the concentration of serum MDA and HSP70 increased significantly as the temperature increased (P<0.05) but the air velocity had no significant effect on serum MDA and HSP70(P>0.05).(5) Taking several essential parameters of sow (parity X3, breed X6, stage of pregnancy X7) as fixed effects and the main environment parameters (temperature X1, humidity X2, air velocity X4, and measure time X5) as random effects, stepwise regression analysis has been performed on skin temperature and respiration rate. The regression equations were obtained as follows:YT=0.679X1+0.02X2-0.341X3-0.707X4+0.035X5+0.143X6+13.411,R2=0.873YRR=4.51X1-1.561X3-11.151X4+6.561X6+1.182X7-96.177, R2=0.67According to the study results, hot-humid environment is detrimental to pigs in terms of feeding behavior, growth and health. Under a condition of heat stress, pigs depend on the central nervous system regulation to adapt to the hostile situation. Once the temperature and humidity exceed adaptable range of pig, heat stress could cause physiological and biochemical imbalances and inhibition of the excitability of appetite center, thus affecting the body’s normal function and performance. Meanwhile in the southwestern Chongqing region, typical extreme hot-humid climate that is usually out of the heat balance adjustment range of pig is quite common. Therefore, in order to improve feeding behavior and production of pigs during the hot summer, we should reduce its degree of heat stress by increasing ventilation and taking other measures. |
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