Effects Of Astragalus Polysaccharide On Growth Performance,antioxidant And Intestinal Health Of Weaned Rabbits

The purpose of this experiment was to investigate the effects of different levels of APS in diets on growth performance,organ index,meat quality,serum biochemical indices,immune performance,antioxidant capacity,nutrient apparent digestibility and intestinal function of young weaned rabbits.To provide the experimental basis for the rational application of Astragalus polysaccharide in meat rabbit production practice.A total of 240 well-grown 35-day-old weaned rabbits with similar body weight were randomly divided into 4 groups(group Ⅰ(control group),group Ⅱ,group Ⅲ and group Ⅳ)with 6 replicates per group and 10 rabbits per replicate.Piglets in group Ⅰwere fed a basal diet,while those in groups Ⅱ,Ⅲ and Ⅳ were fed the basal diet supplemented with 100 mg/kg,200 mg/kg and 400 mg/kg APS,respectively.The pretest lasted for 7 days and the test lasted for 35 days.The results show that:(1)The final weight(FBW),average daily gain(ADG)and feed to gain ratio(F/G)of weaned rabbits were significantly affected by APS supplementation.Compared with the control group,ADG of weaned young rabbits in group Ⅲ was significantly increased(P<0.05),and F/G was significantly decreased(P<0.05);The FBW of weaned rabbits in groups Ⅲ and Ⅳ was significantly increased(P<0.05).(2)Dietary supplementation of APS significantly affected the thymus index,sac index and perirenal fat of weaned rabbits.Compared with the control group,the thymus index of weaned young rabbits in groups Ⅱ and Ⅲ was significantly increased(P<0.05),and perirenal fat was significantly increased(P<0.01);The round sac index of weaned rabbits in group Ⅳ was significantly increased(P<0.05).(3)Astragalus polysaccharide supplementation significantly affected muscle brightness L* and redness a* in weaned rabbits.Compared with the control group,muscle brightness L* in group Ⅱ was significantly increased(P<0.05);Muscle redness a* in group Ⅲ was significantly increased(P<0.05).(4)Dietary astragalus polysaccharide significantly affected the contents of blood glucose(GLU),albumin(ALB),triglyceride(TG),alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in serum of weaned rabbits.Compared with the control group,GLU content and ALB content of weaned young rabbits in group Ⅲwere significantly increased(P<0.05);The content of TG in weaned rabbits in groupsⅡ and Ⅲ was significantly increased(P<0.01);ALT activity of weaned rabbits in groups Ⅱ,Ⅲ and Ⅳ was significantly decreased(P<0.01);AST activity of weaned rabbits in group Ⅳ was significantly decreased(P<0.05).(5)The contents of immunoglobulin A(Ig A)and immunoglobulin G(Ig G)in serum of weaned rabbits were significantly affected by APS supplementation.Compared with the control group,the serum Ig A and Ig G contents of weaned rabbits in groups Ⅱ,Ⅲ and Ⅳ were significantly increased(P<0.01).(6)The supplementation of APS significantly affected the total antioxidant capacity(T-AOC)and catalase(CAT)activities in serum of weaned rabbits.Compared with the control group,the serum T-AOC of weaned piglets in groups Ⅲ and Ⅳ was significantly increased(P<0.05);Serum CAT activity of weaned rabbits in groups Ⅱand Ⅲ was significantly increased(P<0.01);CAT content in group Ⅳ was significantly increased(P<0.05).(7)The digestibility of dry matter(DM),organic matter(OM),crude fat(EE),crude protein(CP),acid detergent fiber(ADF)and gross energy(GE)of weaned rabbits was significantly affected by the addition of APS in the diet.Compared with the control group,the digestibility of DM and OM in group Ⅲ was significantly increased(P<0.05);The digestibility of EE and CP in group Ⅳ was significantly decreased(P<0.05);ADF digestibility in group Ⅱ was significantly increased(P<0.05);The digestibility of ADF in groups Ⅲ and Ⅳ was significantly increased(P<0.01),and the digestibility of GE in group Ⅲ was significantly increased(P<0.01).(8)Dietary supplementation of astragalus polysaccharide significantly affected villus height,crypt depth and pile crypt ratio in small intestine of weaned rabbits.Compared with weaned rabbits in control group,duodenal villus height and chaincrypto ratio of weaned rabbits in groups Ⅲ and Ⅳ were significantly increased(P<0.01).The villus height of weaned rabbits in group Ⅳ was significantly increased(P<0.05),the crypt depth of jejunum in groups Ⅲ and Ⅳ was significantly decreased(P<0.01),and the ratio of pile to crypt was significantly increased(P<0.01).The crypt depth of ileum of weaned rabbits in groups Ⅱ,Ⅲ and Ⅳ was significantly decreased(P<0.01).The ileum chain-crypt ratio of weaned rabbits in group Ⅱ was significantly increased(P<0.05);The ileum chain-crypt ratio of weaned rabbits in groups Ⅲ and Ⅳwas significantly increased(P<0.01).(9)Dietary supplementation of astragalus polysaccharide significantly affected the relative expression levels of ZO-1 m RNA and SGLT1 m RNA in duodenum and jejunum of weaned rabbits.Compared with weaned rabbits in control group,the m RNA relative expression level of duodenal tight junction protein ZO-1 in weaned rabbits in group Ⅳ was significantly up-regulated(P<0.01).The relative expression level of ZO-1 m RNA in jejunum in groups Ⅲ and Ⅳ was significantly up-regulated(P<0.01).Compared with weaned rabbits in control group,the m RNA relative expression level of duodenal glucose transporter SGLT1 in weaned rabbits in groups Ⅲ and Ⅳ was significantly up-regulated(P<0.01).The m RNA relative expression levels of glucose transporter SGLT1 in jejunum in groups Ⅱ,Ⅲ and Ⅳ were significantly up-regulated(P<0.01).In conclusion,dietary APS can significantly improve the growth performance,organ index and meat quality of weaned rabbits,enhance the serum biochemical,immune and antioxidant capacities,and improve the apparent digestibility of nutrients and Expression of genes related to intestinal function,and the appropriate supplemental level is 200 mg/kg.