Effect Of Relative Humidity On Growth Performance,Immune Function And Respiratory Mucosal Barrier Of Broilers

In this study,the effects of relative humidity on the growth performance,immune function and respiratory mucosal barrier of AA broilers were studied by simulating different humidity in poultry house,to provide data support for the environmental control of livestock and poultry house and the development of healthy breeding of broiler.The single factor randomized design was used in the experiment,270 1-day-old AA broiler chickens were randomly divided into 3 treatments with 6 replicates of 15 broilers per replicate.The treatments were: control group(60% RH),low humidity group(30% RH)and high humidity group(90% RH).The experiment was conducted in artificial climate chamber in state key laboratory of animal nutrition.The experimental period was 42 days.Experiment 1: Effects of different relative humidity on growth performance and meat quality of broilers.Results showed that: 1)Compared with the control group(60% RH),the average daily gain(ADG)in low humidity group(30% RH)significantly decreased(P<0.05)and the feed/gain ratio(F/G)significantly increased(P<0.05)in broilers from 1 to 21 days of age(P<0.05).ADG,F/G and ADFI in high humidity group(90% RH)show no significantly difference(P>0.05).ADFI and ADG in the low humidity group(30% RH)were significantly lower than those in the control group(P<0.05),and ADFI in the high humidity group(90% RH)was significantly lower than that in the control group(P<0.05)of broilers from 1 to 21 days of age.As can be seen from the entire period(1 ~ 42 days),the ADFI and ADG of the low-humidity group were significantly lower(P<0.05)and the feed/gain ratio were increased(P<0.05)than those in the control group(60% RH).ADFI and ADG in the high-humidity group were reduced and the feed/gain ratio were increased,but no significant difference were observed(P<0.05).2)Compared with the control group,the high-humidity group significantly reduced the dressing rate of 42-day-old chickens(P<0.05).3)Compared with the control group,the high humidity treatment significantly improved the cooking loss(P<0.05)and reduced the shear stress(P<0.05)of the 21-day-old broilers(P<0.05).Low humidity or high humidity is not conducive to the growth of broilers,in which low humidity significantly decreased average daily gain and feed conversion,and high humidity significantly affected slaughter performance and meat quality.Experimrnt 2: Effects of different relative humidity on blood chemical indexes and immune function in broilers.The results showed that: 1)Compared with the control group,at 21 days of age,low humidity group significantly reduce the number of white blood cells and lymphocyte count(P<0.01);the number of platelets were significantly higher in low humidity group than that of high humidity group.At 42 days of age,white blood cell counts were significantly lower in low humidity and high humidity groups than control group(P<0.05).2)At 21 days of age,the serum urea nitrogen content in the low humidity group and the high humidity group was significantly higher than that in the control group(P<0.05),while the total cholesterol content in the high humidity group was significantly lower than that in the control group and low humidity group(P<0.05).At 42 days of age,the serum total protein,uric acid and urea nitrogen in the low humidity group and high humidity group were higher than those in the normal humidity group,while the content of serum albumin,lysozyme,total cholesterol and triglyceride Lower than the normal humidity group.3)Compared with the normal control group,the serum superoxide dismutase and the total antioxidant capacity of the broilers in the low humidity group at 21 days of age were significantly lower than those of the normal control group(P<0.05).At the age of 42 days,the activity of serum superoxide dismutase and total antioxidant capacity in the low humidity group were significantly lower than those in the control group(P<0.05),while the the content of malondialdehyde was significantly increased(P<0.05);Compared with the normal control group,serum total antioxidant capacity in the high humidity group were significantly decreased(P<0.05)and the the content of malondialdehyde was significantly increased(P<0.05).4)The spleen index of broiler chickens in low humidity group was significantly lower than that of high humidity group at 21 days of age(P<0.05);Besides,the concentration of IFN-γ,TNF-α and IL-6 in high humidity group was significantly higher than control group on d 21(P<0.05).Compared with the control group,at the age of 42 days,the content of IgA in low humidity group and the content of IgM in high humidity group were significantly lower(P<0.05).In conclusion,long-term low humidity or high humidity changed in blood white blood cell count,total cholesterol and blood urea nitrogen content and other blood physiological and biochemical parameters,reduced immune function.Experimrnt 3: Effects of different relative humidity on the structure and diversity of microbial flora in the trachea of broilers.The results showed that: 1)DGGE profiles analysis showed that with the increase of age,the respiratory tract flora of broilers were increasing.There were not only common bands but also individual bands in the six groups at different ages and different humidity,but the brightness of bands varied,indicating that the colonies colonized in different age and different humidity environment were difference.2)At 21 days of age,shannon index and richness of low humidity group and high humidity group were lower than that of control group;the homogeneity of high humidity group was higher than that of control group,while that of low humidity group was lower than that of control group.At 42 days of age,the Shannon index and richness of low humidity group were lower than that of control group;the Shannon index,evenness and richness of high humidity group were higher than that of control group.3)DGGE profiles stripe sequence analysis showed that the common bacteria in the trachea of different humidity treatments were Pseudomonas syringae,Pseudomonas savastanoi and Faecalibacterium prausnitzii.At 21 days of age,the specific bands were Lactobacillus johnsonii and Lactobacillus reuteri of contral group.The results of this study indicate that relative humidity impact the community structure and diversity of tracheal flora in broilers,and the extent of effect varies with the different humidity.Experimrnt 4: Effects of different relative humidity on antioxidant capacity and mucosal barrier of trachea in broilers.Results showed that: 1)Activity of glutathione peroxidase,superoxide dismutase and total antioxidant capacity in trachea tissue of low humidity group was significantly lower than control group on d 21(P<0.05),and glutathione peroxidase of high humidity group and low humidity group were both lower than control group on d 42(P<0.05).2)Meanwhile,compared with control group,the tight junction proteins expression of Claudin1,ZO-1 and Occludin mRNA in trachea tissue of the low-humidity group were lower on d 42(P<0.05);and ZO-1 mRNA expression in high humidity group was lower on d 42(P<0.05).3)Muc 5AC and Muc 5B mucins,and apoptosis protein Caspase-3 mRNA expression in trachea tissue of low humidity group were higher than control group on d 21,and Muc 5B mRNA expression were higher on d 42.Muc 5B mRNA expression in trachea tissue of high humidity group was higher than control group on d 21.These results revealed that abnormal humidity environment could reduce antioxidant capacity of broilers and damage to the respiratory mucosal barrier in broiler chickens.In summary,the results showed that abnormal humidity environment reduced the growth performance and immune function;damage the respiratory mucosal barrier of broiler.