Effects Of Relative Humidity On Physiological And Metabolic Functions And Performance In Broiler Chickens At Different Moderate Temperatures

With the development of wet curtain cooling technology,the situation of the high temperature environment of the barn is less in the actual production,but the moderate environment?below 31??is often found.In this paper,the relative humidity is applied to the physiological and metabolic functions and performance of broilers under different moderate temperature and aims to provide a scientific basis for the refinement and comfort of poultry farming.The paper includes two major experiments,four aspects of the study,the main contents are as follows:1.Effects of environmental relative humidity at intermittent moderate temperatures on body temperature,acid-base balance,performance of broilers.A total of 360 22-year-old AA broilers were allotted into six environment chambers,each chamber contained six cages with ten birds per cage?with five males and five females?,and each cage as a replicate.The pre-test period lasted for 7 days and broilers were kept at 20?and 60%relative humidity.When broilers were 29-day-old,the temperature of?,?,?group were at 26?,the temperature of?,?,?group were at 31?,while regulating the relative humidity to 35%,60%,85%??,?,?and?,?,??,respectively;the period of each day were kept six hours,at 10:00¹6:00,after the period,broilers were kept at 20?and 60%relative humidity.The trial lasted for 14 days.The results showed as follows,1)average daily food intake?ADFI?,average daily gain?ADG?in?group showed significant higher than that in other groups?P<0.05?;ADFI and ADG in?group showed significant lower than that in other groups?P<0.05?;no significant difference F/G was found among the groups?P>0.05?.2)the first day,the third day and the tenth day,core temperature and skin temperature in?group showed significant higher than that in other groups?P<0.05?,skin temperature in?group showed significant higher than that in?and?group?P<0.05?;the first day,core temperature in?group showed significant higher than that in?and?group?P<0.05?,the third day and the tenth day,there is no significant difference among the three groups?P>0.05?.3)pH and pO₂ in?group showed significant lower than that in other groups?P<0.05?,no significant difference between pCO₂ and HCO₃^-was found among the groups?P>0.05?.In conclusion,at the intermittent thermal of 26?,31?,compared with60%group,85%and 30%group could change the body temperature,acid-balance and performance.And at the different extent moderate heat stress,different relative humidity levels would produce different effects on that.2.Effects of relative humidity on physiological and metabolic functions and performance in broiler chickens at gradually increasing temperatures.2.1.Effects of relative humidity at gradually increasing temperatures on body thermo regulation and content of heat shock protein 70 in hypothalamus of broiler chickens.One hundred and eighty 21-day-old Arbor Acres?AA?broiler chickens were allotted into environment controlled chambers and randomly assigned to three groups with six replicates per group and ten broilers per replicate?males and females in half?.The pre-test period lasted for 7 days and birds were kept at 20?and 60%RH.The test period lasted for 15 days,when broiler chickens were 28days of age,RH of three groups was regulated to 35%,60%and 85%,respectively,and the temperature was 20?yet.The experiment consisted of 5 consecutive trials with 3 days per consecutive trial,the temperature of three groups was gradually increased by 3?finishing within half an hour at 10:00 of the first day every consecutive trial and started from the second consecutive trial,and the temperatures of the 5 consecutive trials were 20,23,26,29 and 32?,respectively.The results showed as follows:1)the respiratory frequency of broiler chickens in the 85%RH group was significantly higher than that in the 60%RH and 35%RH groups?P<0.01?,and the respiratory frequency in the 60%RH group was significantly higher than that in the 35%RH group?P<0.01?.The core body temperature of broiler chickens in the 85%RH group was significantly higher than that in the 60%RH group?P<0.05?.The skin temperatures of leg and flipper of broiler chickens in the 35%RH group were significantly higher than those in the 60%RH and 85%RH groups?P<0.01?,and the skin temperatures of comb,earlobe and eyelid in the 35%RH and 60%RH groups were significantly higher than those in the 85%RH group?P<0.01?.2)The activity of alkaline phosphatase?AKP?in serum of broiler chickens in the 85%RH group was significantly higher than that in the 60%RH and 35%RH groups?P<0.05?,and the activity of creatine kinase?CK?in serum of broiler chickens in the 85%RH and 35%RH groups was significantly higher than that in the 60%RH group?P<0.05?.There were no significant effects of RH at gradually increasing temperatures on the activities aspartate transaminase?AST?and lactate dehydrogenase?LDH?in serum of broiler chickens?P>0.05?.3)The content of 3,5,3'-triiodothyronine?T₃?in serum of broiler chickens in the 85%RH group was significantly higher than that in the 35%RH group?P<0.05?,the content of 3,5,3',5'-tetraiodothyronine?T₄?in serum in the 35%RH and 85%RH groups was significantly higher than that in the 60%RH group?P<0.05?,and the content of cortisol?CORT?in serum in the 60%RH and 85%RH groups was significantly higher than that in the 35%RH group?P<0.01?.4)The content of HSP70 in hypothalamus of broiler chickens in the 35%RH group was significantly lower than that in the 60%RH and 85%RH groups?P<0.05?.In conclusion,at the15-day 20 to 32?gradually increasing temperatures,high humidity?85%?and low humidity?35%?regulate the body heat balance of broiler chickens at 28 to 42 days of age in different ways and extent.2.2.Effect of changes in relative humidity at increasing temperatures on growth performance,glucose metabolism,and avian uncoupling protein mRNA expression in broilers.Material method was the same with trial 2.1.Glucose,hepatic glycogen,and muscle glycogen contents,av UCP mRNA expression,average daily gain?ADG?,average daily feed intake?ADFI?,average daily water consumption,and feed-to-gain ratio?F:G?were analyzed.The animals were provided feed and water ad libitum.Throughout the experimental period,compared with the 60%RH group,the ADFI of the 85%RH group decreased by 37.91%?P<0.05?,whereas the ADG of the 35%RH and 85%RH groups significantly decreased by 21.47%and 25.68%,respectively?P<0.05?,and the average daily water consumption of the 85%RH group significantly decreased by 78.62%?P<0.05?.Glucose content was lowest at 60%RH group among the three groups?P<0.0001?,hepatic glycogen was lowest at 85%RH group among the three groups?P<0.05?,and muscle glycogen was highest at60%RH group among the three groups?P<0.05?;and the av UCP mRNA expression of the 85%RH and 35%RH groups was significantly increased by 48%and 51%?P<0.05?,respectively,compared to that of the 60%RH group.Based on these results,we conclude that at gradually increasing temperatures,very high?85%?and low humidity?35%?disrupt the energy balance in broilers and decrease their production performance,which is not conducive to animal welfare.Thus,60%RH is the best choice for the 28⁴2-old broiler at gradually increasing temperatures?from 20?to 32??.2.3.Based on the ultra-high performance liquid chromatography combined with quadrupole-time of flight mass spectrometry of relative humidity under gradually increasing temperatures of broiler fecal metabolomics research.high performance liquid chromatography and quadrupole-time of flight mass spectrometry?UHPLC-Q-TOF MS?metabolomics techniques used to study the relative humidity?RH?of broiler fecal metabolites under gradually increasing temperatures?Ta?.Principal component analysis?PCA?and partial least squares discriminant analysis?PLS-DA?were used to distinguish potential markers from feces in low,wet and high humidity groups.The data were normalized by the total peak area,PCA and PLS-DA,respectively.Based on the degree of projection projection VIP>1 and P<0.05,and found,respectively,in HILIC and HSS T3 positive and negative ion mode scanning to give each group may bio markers wherein,HILIC positive ions are 10 potential markers,negative ions to give 12 potential bio markers;HSS T3 positive ions are 5 potential bio markers anion get 9 potential bio markers.And further verified by cluster analysis and KEGG pathway analysis,the metabolites we obtained above could be involved in the metabolism of beta-alanine,pyrimidine,starch and sucrose,galactose,amino sugars and nucleotide sugars,glucagon signaling pathways,glycolysis/Primary bile acid synthesis,taurine and other metabolic pathways.In conclusion,1)at the intermittent thermal of 26?,31?,compared with 60%group,85%and35%group could change the body temperature,acid-balance and performance.And at the different extent moderate heat stress,different relative humidity levels would produce different effects on that;2)at the 15-day 20 to 32?gradually increasing temperatures,high humidity?85%?and low humidity?35%?regulate the body heat balance of broiler chickens at 28 to 42 days of age in different ways and extent;very high?85%?and low humidity?35%?disrupt the energy balance in broilers and decrease their production performance,which is not conducive to animal welfare;3)in HILIC and HSS T3positive and negative ion mode scanning to give each group may bio markers wherein,HILIC positive ions are 10 potential markers,negative ions to give 12 potential bio markers;HSS T3 positive ions are five potential bio markers anion get nine potential bio markers.And further verified by cluster analysis and KEGG pathway analysis,the metabolites we obtained above could be involved in the metabolism of beta-alanine,pyrimidine,starch and sucrose,galactose,amino sugars and nucleotide sugars,glucagon signaling pathways,glycolysis/Primary bile acid synthesis,taurine and other metabolic pathways.