| The study was divided into two parts which included antibacterial tests of medium chain triglyceride(MCT)in vitro and animal experiments in vivo.The purpose of this experiment is to systematically evaluate the effects of MCT replacing soybean oil in diet on growth performance,serum immune and oxidative function and intestinal health of young rabbits,to further determine the appropriate level of MCT in the diet of young rabbits,and to provide a theoretical basis and scientific basis for taking effective nutritional measures in reducing weaning stress and diarrhea and improving production performance of rabbits.Experiment 1: The aim of this experiment was to evaluate the inhibition effect of MCT for different bacteria in vitro.We selected finished powdered product of MCT,including caproic acid(C6:0),caprylic acid(C8:0)and capric acid(C10:0),and fatty acid content greater than 45%.Five kinds of common pathogenic bacteria in rabbits have been selected,including Escherichia coli(ATCC25922),Pasteurella multocida(CVCC393),Staphylococcus aureus(ATCC6538),Bordetella bronchiseptic(ATCC4617)and Streptococcus pyogenes(CMCC32210).The antibacterial activity of MCT was evaluated by measuring the diameter of the zones of inhibition against the tested bacteria.The results are as follows:(1)for the five common pathogenic bacteria in rabbits,MCT had bacteriostatic effect on each one of them,but the effect is significantly correlated with the species of bacteria.MCT had a strong bacteriostatic effect on Escherichia coli,Staphylococcus aureus and Streptococcus bovis,while the bacteriostatic effect on Pasteurella multocida and Bordetella bronchiseptica is average,especially Bordetella bronchiseptic.(2)Escherichia coli,Pasteurella multocida and Bordetella bronchiseptica belong to Gram-negative bacteria,and Staphylococcus aureus and Streptococcus b.haemolyticus belong to Gram-positive bacteria,therefore,the bacteriostatic effect of MCT on Gram-positive bacteria is stronger than that of Gram-negative bacteria.Experiments 2: This experiment was to study the effects of different levels MCT on growth performance,immune and oxidative function and intestinal health of young rabbits.A total of 600 young rabbits with similar body weight at 35 d of age were randomly divided into 5 groups with 6 replicates in each group and 20 rabbits in each replicate(half male and half female).The control group was fed a basal diet containing2,400 mg/kg soybean oil,the experimental groups were substituted with 600,1,200,1,800 and 2,400 mg/kg MCT respectively.The whole trial period lasted for 48 days(7-day pre-feeding period and 42-day trial period).The results showed that:(1)ADFI and F/G were significantly lower in 1,200 mg/kg MCT groups than in the control group(P < 0.05).Compared with the control group,the diarrhea rate of young rabbits in 1,800 mg/kg and 2,400 mg/kg MCT groups were significant decreased and the survival rate were increased significantly(P < 0.05).During the experiment,there was no statistical difference in ADG values among the five groups(P > 0.05).(2)Serum immunoglobulin of Ig A,Ig M and Ig G were significantly higher in all MCT-treated groups than the control group,and serum Ig A increased significantly with increasing levels of MCT substitution(P < 0.05).Serum IL-6 levels were significantly lower in all experimental groups compared to the control group only in the 1,800 mg/kg MCT group(P < 0.05).Serum CAT and SOD levels significant differences were found only at the addition levels of 1,800 and 2,400 mg/kg MCT(P < 0.05).Compared with the control group,the serum T-AOC content in 2,400 mg/kg MCT group was significantly increased(P < 0.05),but there was no significant difference serum T-AOC content in600,1,200 and 1,800 mg/kg MCT groups and the control group(P > 0.05).(3)Compared with the control group,the height of jejunal villi was significantly increased in 1,800 mg/kg and 2,400 mg/kg MCT groups,and the height of jejunal villi of was significantly increased in 2,400 mg/kg MCT group(P < 0.05).(4)Compared with the control group,the apparent digestibility of CP in 1,200 and 1,800 mg/kg MCT groups was significantly increased(P < 0.05).The substitution of soybean oil with MCT had no significant effect on the apparent digestibility of DM and CF in young rabbits(P >0.05).(5)Compared with the control group,Chao1 index of cecal flora in 2,400 mg/kg MCT group was significantly increased(P < 0.05),but MCT had no significant effect on other alpha diversity indices and beta diversity indices(P > 0.05).(6)Compared with the control group,at phylum level,the abundance of Bacteroidetes increased significantly in 1,800 and 2,400 mg/kg MCT groups,and the abundance of Actinobacteria and Verrucomicrobia decreased significantly in 1,800 mg/kg MCT group(P < 0.05).At the family level,a significant decrease in the colony abundance of Ruminococcaceae and a significant increase in the level of Lachnospiraceae were observed in the 2,400 mg/kg MCT group(P < 0.05).In addition,the colony abundance of Muribaculaceae significantly increased at the addition level of 1,800 and 2,400mg/kg MCT(P < 0.05).At the genus level,MCT only decreased the abundance of the Subdoligranulum flora and there was no significant difference among the experimental groups(P > 0.05).It can be concluded from the above experiments that the in vitro antibacterial test and animal test showed MCT has obvious in vitro bacteriostatic effect.MCT has significant effects on the growth of young rabbits,significantly improves the blood immunity and antioxidant levels,the height of small intestinal villi and the digestibility of crude fat,and it has certain influence on the cecum intestinal microorganism. |
PDF Full Text Request