Effects Of Dietary Bacillus Coagulans On Growth Performance,Gastrointestinal Physiology And Immunity In Meat Rabbits

Bacillus coagulans has received particular interests in animal nutrition research due to probiotic properties and other health benefits in animals.The main aim of the present experiment was to study the effects of dietary supplementation with B.coagulans on the productive performance,gastrointestinal physiology and immunity of the meat rabbits.The experiment was designed using a single-factor randomized trial with six treatment groups.The control group was fed on standard basal diet with no supplementation.Rabbits in the 2-6 group received the same basal diet supplemented with 0.5×10~6,1×10~6,2×10~6,4×10~6 and 8×10~6 cfu/g B.coagulans.Growth trail:252 meat rabbits with average body weight of 907.02±13.33g randomly divided into 6 groups of each 21 replicates,2 rabbits in each replicate.The adaptation period lasted for 5 days and the formal period lasted for 35 days(early stage:1-14d,later stage:15-35d).At the end of the experimental period,blood and tissue samples were collected from 4 animals per group.Digestion trial:60 meat rabbits at 42 days old with average body weight of 1086.00±25.00g randomly divided into 6 groups of each 10 replicates,1 rabbits in each replicate.The adaptation period lasted for 7 days and the formal period lasted for 4 days,the nutrient digestibility was measured.The results showed as follows:(1)Dietary supplementation of 0.5×10~6cfu/g B.coagulans decreased the feed/gain(F/G)of rabbits in the earlier stage by 11.35%in the earlier stage(P<0.05).Whereas no significant effect of B.coagulans was observed on average daily weight gain(ADG)and average daily feed intake(ADFI)in early stage,later stage,and whole experimental period(P>0.05).(2)The inclusion of 0.5×10~6cfu/g and 1×10~6cfu/g B.coagulans significantly decreased the health risk of meat rabbits by 50.00%,50.00%in the whole experimental period respectively(P<0.05);a trend was observed where the presence of B.coagulans decreased the morbidity and mortality rate of meat rabbits(P<0.10).(3)The apparent digestibility of CP in meat rabbits fed with dietary supplementation of 2×10~6cfu/g,8×10~6cfu/g B.coagulans significantly increased(P<0.05);2×10~6,4×10~6 and 8×10~6cfu/g increased the apparent digestibility of EE(P<0.01);0.5×10~6 and 1×10~6cfu/g B.coagulans decreased the TC content of serum(P<0.05);4×10~6cfu/g decreased the TG content of serum(P<0.05).(4)Dietary supplementation of 1×10~6 and 2×10~6cfu/g B.coagulans significantly increased the duodenal villus length and the cashmere recession ratio of meat rabbits(P<0.05).However,no difference was found in jejunum and ileum.Dietary supplementation of 1×10~6cfu/g B.coagulans decreased the content of NH3-N in cecal chime(P<0.05);4×10~6cfu/g decreased the quantity of E.coli in cecal chime(P<0.05);8×10~6 cfu/g increased the quantity of Lactobacillus in cecal chime(P<0.05).(5)The addition of B.coagulans in diet promoted the immune and antioxidant capacity of meat rabbits.Dietary supplementation of 4×10~6cfu/g B.coagulans increased the IgM content of serum(P<0.05).Moreover,0.5×10~6 and 1×10~6cfu/g B.coagulans increased the SIgA content of Jejunum mucosa(P<0.01)and enhanced the activities of T-AOC,T-SOD and GSH-PX in jejunum and liver of meat rabbits.Whereas,there was no significant effect on serum antioxidant capacity and MDA content in serum.In conclusion,dietary supplementation of B.coagulans significantly increased feed conversion rate and reduced the mortality and health risk index of rabbits during the growth and fattening period.This improvement in meat rabbits could be related to beneficial changes in intestinal development,amylase activity of duodenal and lipase activity of jejunum,digestion and absorption of nutrients,the interior environment and microecological balance of caecum,and improvement of immune and antioxidant function.In our experiment,general growth performance,health risk index,immunity and antioxidant capacity as a recommendation,the appropriate supplemental level of B.coagulans in meat rabbit diet was 1×10~6cfu/g.