| After the prohibition of antibiotics,the application of new microbial feed additives in livestock and poultry has attracted more and more attention.Bacillus subtilis and Yeast cell wall are widely used as feed additives.Previous laboratory studies suggest that Bacillus subtilis can inhibit the growth of harmful bacteria in the intestine and establish a good intestinal microbial environment by regulating the intestinal microbial barrier function of aged laying hens.In addition,Bacillus subtilis can also reduce intestinal inflammatory response,down-regulate the level of systemic inflammatory factors and affect bone metabolism,so as to protect bone property.However,most of the studies on laying hens are in the laying stage.It is not clear whether feeding Bacillus subtilis,Yeast cell wall and mixtures in the early stage can establish a good health state and promote the economic benefits of laying hens in the early stage of laying.The purpose of this experiment was to study the effects of Bacillus subtilis and Yeast cell wall separately or in combination on growth performance,performance and immune function of laying hens at growing stage and early laying stage,and to provide scientific basis for the application of Bacillus subtilis and Yeast cell wall in laying hens.A total of 160 1-day-old healthy Haylan Grey egg chicks with similar body weight were randomly divided into 4 groups: control group(CG)and Bacillus subtilis group(BS).The Yeast cell wall group(YCW)and the mixed group(MG).The control group was fed the basal diet.Bacillus subtilis group was fed the basal diet supplemented with0.5 g/kg Bacillus subtilis.Yeast cell wall group was fed the basal diet supplemented with 2 g/kg Yeast cell wall.The mixed group was fed the basal diet supplemented with0.5 g/kg Bacillus subtilis and 2 g/kg Yeast cell wall.There were 8 replicates in each group and 5 animals in each replicate.The animals were continuously fed for 170 days.1.In order to study the effects of Bacillus subtilis and Yeast cell wall on the growth performance of laying hens,at 9:00 a.m.on the 110 th and 170 th days,one chicken was taken for each repetition,and its body weight was measured.After the laying hens were anesthetized with 30 mg/kg pentobarbital sodium,and subjected to cervical dislocation,their muscle stomachs and glandular stomachs were weighed for growth organ index analysis.Duodenum,jejunum and ileum were soaked in 10% formalin solution and fixed.Morphological changes of each intestinal segment were observed by histopathologic section-HE staining technique.The blood of laying hens was collected and the content of calcium and phosphorus in serum was detected by automatic biochemical analyzer.After laying hens were killed 170 days later,the right femur and tibia of each laying hens were collected to obtain the weight,length and volume of the femur and tibia.The bone strength and bone density were measured using a universal testing machine and bone density detector.The results showed: compared with CG group,there were no significant differences in body weight,muscular stomach index and glandular stomach index of laying hens in BS group,YCW group and MG group(P > 0.05).At 110 days,compared with CG group,the jejunal crypt depth and ileum crypt depth in BS,YCW and MG groups were significantly decreased(P < 0.05),the ratio of jejunal villi to jejunal crypt in BS group was significantly increased(P < 0.05),and the ratio of ileum villi to ileum crypt in BS,YCW and MG groups was significantly increased(P < 0.05).At 170 days,compared with CG group,duodenal crypt in BS,YCW and MG groups was significantly decreased,and the ratio of duodenal villi to duodenal crypt and jejunal villi to jejunal crypt in BS and MG groups was significantly increased(P < 0.05).Bacillus subtilis and Yeast cell wall had no significant effects on serum calcium and phosphorus contents(P > 0.05).Compared with the control group,yeast cell wall significantly increased the length,weight,and volume of the femur(P <0.05),while Bacillus subtilis significantly increased the length of the femur(P < 0.01).2.In order to study the effects of Bacillus subtilis and Yeast cell wall on immune function of laying hens,blood serum and plasma were collected from the heart at 110 and 170 days.Blood factors CD3 molecule,CD4 molecule,CD8 molecule,C-reactive protein(CRP),interleukin-6(IL-6),immunoglobulin M(IgM),tumor necrosis factor-α(TNF-α)were detected by ELISA.The number of heterophil granulocytes,eosinophils,basophil granulocytes,lymphocytes and monocytes was calculated by observing blood smears with Wright-Giemsa staining.The thymus,spleen and bursae of Fabricius of laying hens were collected and analyzed for the index of immune organs.The results showed: During the whole experiment,there were no significant differences between Bacillus subtilis and Yeast cell wall in the number of heterophil granulocyte,eosinophilic cells,basophil cells,lymphocytes and monocytes,as well as the contents of CRP,CD8,CD3 and IL-6(P > 0.05).At 110 days,compared with BS group,CD4 content in YCW group was significantly increased(P < 0.05),CD4 content in CG and MG groups was increased but not significant(P > 0.05),compared with CG group,the contents of TNF-α and IgM in MG group were significantly increased(P < 0.05),and the contents of TNF-α and IgM in YCW group were increased but not significant(P >0.05).At 170 d,there were no significant differences in the contents of CD4,IgM and TNF-α among all groups(P > 0.05).3.In order to study the effects of Bacillus subtilis and Yeast cell wall on the performance of laying hens,eggs were collected from 9:00 am to 10:00 am on 166-169 d.The daily egg production and the number of broken eggshells were recorded,and one egg sample was randomly collected in each replicate.Using eggshell color reflector,eggshell strength measurement,vernier caliper,egg quality analyzer to determine eggshell color,eggshell strength,eggshell thickness,egg weight,egg height,egg yolk color,Haugh unit.The results showed: Bacillus subtilis and yeast cell wall had no significant effects on laying rate,eggshell breaking rate,eggshell strength and Haugh unit of laying hens at growing stage and early laying stage(P > 0.05).Compared with the control group,Bacillus subtilis,yeast cell walls,and mixtures significantly improved egg weight,yolk color(P < 0.01),and eggshell color(P < 0.05),The yeast cell wall and mixture significantly increased the eggshell thickness(P<0.01).In conclusion,Bacillus subtilis,Yeast cell walls,and mixtures can all reduce inflammation,improve intestinal morphology,promote femoral growth,and improve egg quality.Bacillus subtilis protects the body from inflammation,and Yeast cell walls resist inflammation by increasing IgM levels.Bacillus subtilis can maintain the morphology of jejunum tissue at all stages,and Yeast cell walls appear to be more conducive to promoting bone growth and improving egg quality,especially egg shell thickness.The combined use of Bacillus subtilis and Yeast cell wall complex was not significantly better than that of single use,but it had positive effects on all indexes,which indicated that the single or combined use of Bacillus subtilis and Yeast cell wall had positive effects on growth performance,immune function and production performance of young laying hens and early laying hens. |
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