The Effects Of Different Rearing Conditions And Adding Probiotics On Gut Microbiota And Physiological And Biochemical Indexes In Laying Ducks

Raising on the plastic mesh floor and on the litter floor are the two main rearing conditions for laying ducks.Among them,the disease rate of the plastic mesh floor ducks was significantly lower than that on the litter floor,which may be due to the differences in the gut microbes of laying ducks in the two rearing conditions.Therefore,we aimed to study the effects of different rearing conditions and adding probiotics on gut microbiota and physiological and biochemical indexes in laying ducks.Firstly,16S rRNA gene sequencing was performed to investigate gut microbiota composition in Shaoxing ducks and Shan partridge ducks respectively.Meanwhile,their performance and physiological and biochemical indexes were also tested.The correlation between gut bacteria and a range of physiological index was analyzed.From the result of the experiment,we concluded scientific rearing conditions,effective types and concentrations of feed additives for farmers to improve poultry productions and peformances.The experiment is divided into two parts:The first part is focusing on the study of effects of different rearing conditions on gut microbiota composition among duodenum,ileum,cecum of Shaoxing duck population at 300 days of age,and then the productive performance,serum physiological and biochemical traits were compared between two rearing conditions.The second experiment is to examine the effect of adding different probiotics on the ileal and caecal microbiota composition in Shan partridge duck population at 500 days of age,and further tested its production performance and the physiological and biochemical indexes.The experimental results were shown as follows:1.Shaoxing ducks in the first study at 300 days of age were raised on the plastic mesh floor(the RPMF group),and on the litter floor(the RLF group),respectively.Firstly,the egg quality traits were compared between RPMF ducks group and RLF group.According to results,we found that egg shell strength values were significantly higher in the RPMF group(P<0.01).No significant differences were observed in others indexes.Secondly,when compared liver physiological and biochemical indexes in two different rearing conditions,we found that the malondialdehyde(MDA)level and the lipopolysaccharide(LPS)level(p<0.01)of the RPMF group were significant increased.While the superoxide dismutase(SOD)(p<0.01)and glutamate-oxaloacetate aminotransferase(AST)activity(p<0.01)were significantly lower than those in the RLF group.However,there were no significant differences observed in T-AOC,ALT,LDH and TNF-a between the two groups.Finally,serum physiological and biochemical indexes of two different rearing conditions were analysed,and we detected that interleukin-4(IL-4)(P<0.01)and estrogen Alcohol-E2(E2)(p<0.01)levels were significantly increased in the RPMF group.However,there are no significant differences in others serum markers.2.Next,we determined to study the composition of intestinal microflora and its association with phenotype in Shaoxing ducks reared on the plastic mesh floor and on the litter floor.A total of 46 and 39 luminal content samples from the duodenum,ileum,and cecum of the ducks reared under the two conditions were analyzed by 16S rRNA gene amplicon sequencing analysis.Proteobacteria(48.66%),Proteobacteria(33.38%),and Bacteroidetes(55.35%)were the dominant components in the duodenum,ileum,and cecum of the ducks reared on the litter floor respectively,while Firmicutes(30.80%),Firmicutes(66.62%)and Bacteroidetes(47.15%)were the topmost components in the duodenum,ileum,and cecum of the ducks reared on the plastic mesh floor.Physiologically,the height of villi and the ratio of villi height to crypt depth in the ileum and duodenum were significantly higher in the ducks rearedon plastic mesh floor.Furthermore,our results demonstrate that the gut microbiota was significantly associated with the duck phenotypes.For example,in the RLF group,which contains the OTUs from genus Epulopiscium,was negatively correlated with the estradiol level.Similarly,in the RPMF group,which contains the OTUs from family Ruminococcaceae,was positively correlated with the estradiol level.Collectively,our results showed that the rearing floor types have an important effect on the gastrointestinal microbial composition of ducks,which can guide the correct management of poultry and improve the physiological and nutritional status of the host's intestine.3.To evaluate the effects of different types and varied concertrations of probiotics added to the feed of Shan partridge duck.The results showed that:firstly,probiotics did not affect most of the production traits of the Shan partridge ducks,while we found the egg yolk colour value were significantly higher in group B and D(P<0.05),but no significant differences were found in the samples collected at days 30 and 45 of the experiment.Secondly,through the analysis of the physiological and biochemical indexes of serum,we found that the concentration of TP in group B was significantly higher after 15 days of experiment.T-AOC and SOD in the group adding probiotics were higher than that of the control group,but the level of MDA were significantly lower than control group.At the same time,the immunological indexes and sex hormone levels were compared,the results showed that the content of IgA,IgM and IgG were increased through probiotics supplementary(P>0.05).4.16S rRNA gene sequencing analyses was used to decipher the influence of different kinds and different dosage of probiotics on gut microbiota composition of Shan partridge duck.Luminal samples and phenotypes were collected and recorded at four time points according to four feeding combination.Firmicutes(64.32%),Bacteroidetes and Proteobacteria(13.16%and 11.03%)were the three dominant phyla independent of feeding patterns.In the cecum,Firmicutes,Bacteroidetes and Proteobacteria were still dominated but with different abundance(41.14%,43.27%and 6.06%,respectively).Alpha diversity analysis showed that the shannon index in the cecum was significantly higher than that in the ileum(P<0.05),and there was a significant difference in gut microbiota composition between control group and adding probiotics ducks(P<0.05).