Effects Of Carbon Dioxide Concentration On The Production Performance,Blood Biochemical Indexes And Nutrient Metabolism Of Laying Hens

The objective of this study was to examine the effects of different carbon dioxide concentrationson production performance,blood gas index,blood biochemical indicators and lung tissue endothelin gene expression of laying hens in the internal environment of the chicken house in winter of China.18060thweek of age"Dawu Jinfeng"layers were selected,randomly divided into 3 groups,each group of 5replicates,replicate of 12 birds.Group I kept the carbon dioxide concentration at 1 500 mg/m³ for the control group,Group II and III had the carbon dioxide concentration of 3500 mg/m³ and 5 500 mg/m³for the experimental group,and the temperature of the three groups remained at 15°C.The pre-test period is 1 week and the official period is 8 weeks.Research indicates:（1）The effect of carbon dioxide concentration on production performance of laying hens was mainly reflected in feed intake,egg production rate,and feed-egg ratio,and a long time under the influence 5500mg/m³ concentration for a long time had a larger impact.At the 4th weekend of the trial,compared with the control group,the feed intake and the feed-egg ratio of the 5500 mg/m³concentration group was increased,and the change was significant（P<0.05）.Within 5-8 weeks,compared with the control group,the carbon dioxide concentration of 3500 mg/m³ and 5 500 mg/m³ of the experimental group the feed intake was increased（P<0.05）,the egg production rate was decreased.The 5500 mg/m³ group had significant changes（P<0.01）,and the feed-egg ratio was also significantly higher than the control group（P<0.01）.（2）Carbon dioxide concentration has little effect on nutrient metabolism.It was found that on the weekend of the fourth week of experiment,the apparent digestibility of calcium and phosphorus in laying hens was greatly influenced by carbon dioxide,and the apparent digestibility of calcium and phosphorus in laying hens at 5 500 mg/m³ was significantly decreased than in the control group（P<0.05）.At weeks 5-8,the apparent digestibility of crude protein in the 500 mg/m³ and 5 500 mg/m³groups was significantly lower than that in the control group（P<0.05）,and significantly decreased in the 5 500 mg/m³ group（P<0.01）;The apparent digestibility of energy showed a decreasing trend in the whole process（P>0.05）.At weeks 8,crude fat was significantly decreased in the 3 500 mg/m³ group and5 500 mg/m³ group compared with the control group（P<0.01）.The apparent digestibility of calcium and phosphorus also decreased significantly（P<0.05）.（3）Carbon dioxide concentration has a greater impact on egg shell thickness.Compared with the control group,the thickness of eggshells in the 3500mg/m³ and 5500mg/m³ groups began to decrease from the 3rd week（P>0.05）.The thickness of egg shells in the 5 500 mg/m³ trial group was significantly lower than that in the control group at the beginning of the 4th week（P<0.05）,and the eggshell thickness decreased more significantly with time（P<0.01）.The eggshell thickness of the 3 500 mg/m³test group was significantly lower than that of the control group after the 6th week（P<0.05）,and the trend was more pronounced as time went on.（4）Carbon dioxide concentration can affect the body’s blood gas index.At the 4th week,the blood levels of PH of 3 500 mg/m³ and 5 500 mg/m³ test group were significantly lower than those of the control group（P<0.05）;The partial pressure of carbon dioxide in blood was also significantly increased（P<0.05）.At the same time,the HCO₃^-concentration was also significantly increased（P<0.05）.At 8th week,5500mg/m³ group had significantly higher carbon dioxide partial pressure and HCO₃^-concentration（P<0.05）than the control group,but the 3500mg/m³ group had an increasing trend but not significant（P>0.05）.（5）Carbon dioxide concentration can affect serum immunoglobulin and complement levels.In the4th week,IgA,IgM,and IgG in the blood of the 3 500 mg/m³ and 5 500 mg/m³ test groups were significantly lower than those in the control group（P<0.05）.Complement C3,C4 and interleukin IL4,IL10 did not change significantly in the first 4 weeks.At 4 weeks and 6 weeks and 8 weeks,the immune index in the blood showed a decreasing trend.Among them,IgA,IgM,and IgG in the blood of the 3500mg/m³ and 5500 mg/m³ test group were significantly lower than those in the control group（P<0.05）.Complement C3 and C4 were also significantly lower than those in the control group（P<0.05）.（6）Carbon dioxide concentration has a great influence on the expression of endothelin-related genes in lung tissues.At the 4th week,the expression levels of ET-1 and ET-A in the 5 500 mg/m³ test group were significantly higher than those in the control group and 3 500 mg/m³ test group（P<0.05）,while the expression level of ET-B was increasedbut not significant（P>0.05）.The expression levels of ET-1,ET-A,ET-B genes in the 3 500 mg/m³ test group were higher than those in the control group but not significantly（P>0.05）.At week 8,the expression levels of ET-1 and ET-A genes were the same as those of week 4.The expression of receptor ET-B in the 5500 mg/m³ test group was significantly higher than that in the control group and the 3 500 mg/m³ test group（P<0.01）.（7）Carbon dioxide concentration has a great influence on the expression of related genes in the trachea.The tight junction protein claudin1 and tracheal muc2 showed a decreasing trend in each experimental group,and the caspase3 showed increased trend.At the 4th week,the expression of claudin1 and muc2 in the 3 500 mg/m³ and 5 500 mg/m³ test groups was significantly lower than that in the control group（P<0.01）.The expression of caspase³ in the 3500mg/m3 and 5500mg/m³ test groups was higher than that in the control group（P>0.05）.At 8thweek,the expressions of claudin1 and muc2 in the 3 500 mg/m³ and 5 500 mg/m³ test groups were significantly lower than those in the control group（P<0.01）.The expression levels of caspase3 in the 3 500 mg/m³ and 5 500 mg/m³ test groups were significantly higher than those in the control group（P<0.01）.The above test results show that the carbon dioxide concentration has an adverse effect on the production performance,the metabolism of nutrients,the blood immune index,and the lung tracheal mucosa related genes expression of the layers.Under high concentrations of carbon dioxide,the longer the time,the greater the impact on chickens.