Study Of Caecal Microbial Diversity Of Post-weaning Rabbits And Effects Of Two Compound Additives On Intestine Health Of Meat Rabbits

Pathogenic microorganisms can infect rabbits easily and cause severe gastrointestinal diseases, especially within 2~3 weeks after weaning. Antibiotics alternatives, such as probiotics, oligosaccharides and acidifiers, can improve the growth performance and health for animals by maintaining the intestinal microenvironment. The thesis detected the caecal microbial diversity after weaning of meat rabbits and discussed the effects of periodical supplement of two compound additives on the intestine health and growth performance of rabbits. Exp. 1 Caecal Microbiota Analysis of Post-weaning Rabbits using Illumina Miseq Sequencing TechnologyThe current study was conducted to evaluate the caecal bacterial structure of weaned young rabbits by Illumina Miseq sequencing technology. Thirty litters of newborn healthy rabbits with same parity and similar average body weight were used and suckled until weaning(30 days of age) in this experiment. Forty-eight healthy rabbits with similar body weight were selected on the day of weaning. No antibiotics were used in the experimental diet and all rabbits were fed restrictedly from 14 days of age to the end of the trial. Six healthy growing rabbits were randomly selected and slaughtered at 30, 37, 44 and 51 days of age, respectively. Three samples of caecal content at each sampling time were collected for extracting the microbial genomic DNA. Microbial structure of caecal contents were evaluated using Illumina Miseq sequencing technology. The results were showed as follows:(1) The alpha diversity index of caecal bacteria tended to rise with age(P<0.10).(2)The caecal bacteria was consisted of Firmicutes, Bacteroidetes, Proteobacteria, Verrucomicrobia, Chloroflexi and Acidobacteria at the phylum level, and their relative abundance was not affected by age(P>0.05). Ruminococcaceae and Lachnospiraceae were the dominant families in Fimicutes, and Bacteroidetes was predominantly composed by Bacteroidaceae and Porphyromonadaceae. Bacteroides, Barnesiella, Prevotella, Akkermansia and four unclassified genus were the common dominant genera at different age by genera level. The relative abundance of Bacteroides and Parabacteroides on the day of weaning was higher than that at other age(P<0.05).(3) Lactobacillus existed in the caecum, and its relative abundance was not changed by age(P>0.05). Based on the results, it is concluded that the caecal microflora ofrabbithas been established and the relative abundance of Bacteroidesiswas highest at weaning, butmicrobial components tend to be complex after weaning. Exp. 2 Effects of periodical supplement of two compound additives on the intestine health and growth performance of rabbits.We studied the effects of two compound additives(I: B.subtilis+ 2% fructooligosaccharide; Ⅱ: 2% acidifier + 0.6% essential oil) which were supplemented periodically on the growth performance, intestinal microflora, caecal fermentation and duodenal configuration of rabbits in this experiment. Two hundred and eighty-eightnew-born IRA rabbits were randomly separated into 6 groups with 6 replicates per group and 8 rabbits per replicate. Six diets were as follows: control(A, basal diet), antibiotics group(B, 0.1‰ bacitracin zinc), Group C(CompoundⅡwere supplemented throughout the whole experiment), Group D(CompoundI pre-weaning and compoundⅡpost-weaning), Group E(CompoundI pre-weaning and compoundI + Ⅱpost-weaning), Group F(CompoundI pre-weaning, compoundⅡ in the first two weeks post weaning andcompoundI afterwards). The supplementary feeding started from d 15 and the rabbits were weaned on d 35. Onehealthrabbit withaverage body weight was chosen from each replicate and slaughtered. The results show that:(1)The mortality during d 15 ~ 77 was significantly influence by treatment(P<0.05); there’s a decreasing trend(P<0.10) on ADG and mortality during d15-35 by treatment; the diarrhea rate during d 15~35 and d36~77 in F was lower than that in A and B(P<0.05).(2) The caecal pH on d 35 was influenced by treatment(P<0.10); compared to the control, the concentrations of caecal ammoniacal nitrogen and acetic acid were improved in B as well as in the “CompoundI pre-weaning” groups(P<0.05); the concentration of caecal VFA in A was significantly higher than other groups(P<0.05).The caecal fermentation parameters on d 77 were not affected by treatment.(3) The amount of ileal E. coli in B, C and “CompoundI pre-weaning” groups was less than that in A(P<0.05) on d 35; the amount of caecal Bacteroides-Prevotella in E and F was more than that in A, B and C on d 77(P<0.05); the amount of caecal total bacteria on d 77 and caecal E. coli and Bacteroides-Prevotella on d 35 was affected by treatment(P<0.10). 4. The duodenal VCR in all “CompoundI pre-weaning” groups was higher than that in A and C on d 35(P<0.05); the crypt depth in E and F on d 77 was lower than that in A and B(P<0.05), while the VCR was higher(P<0.05). Above all, the supplement of compound I pre-weaning, compoundI and compoundⅡ post-weaning and compoundⅡ in the first two weeks post-weaning and compound I afterwards could improve the intestine health and growth performance.