| The gastrointestinal tract of mammals harbors a community of microbiomes that is critical to host health,which primarily contains bacteria,archaea,anaerobic fungi,and ciliated protozoa.This study conducted four experiments to explore the effects of lambs’age on growth performance,rumen fermentation,serum parameters,and the rumen and rectum bacteria and fungi communities.Meanwhile,we investigated the impact of rumen fluid transplantation on gastrointestinal bacterial communities and growth performance in weaned lambs.Experiment 1 was to research the growth performance,rumen fermentation,and serum parameters in the different growth periods of lambs.Ten lambs with similar birth weights were selected(Hu sheep breed,female,singletons),body weight and serum parameters were monitored at 30,60,90,and 120 days of age,and rumen fermentation was observed at 0,3,10,20,30,45,60,90,and 120 days of age.The results demonstrated that the body weight of lambs was linearly increased with age(P<0.05).The highest(P<0.05)average daily gain(ADG)was found between 30 to 60 days of age and the lowest(P<0.05)ADG was found between 60 to 90 days of age in lambs.Serum concentrations of albumin(ALB),glucose(GLU),and non-esterified fatty acid(NEFA)were higher at 30 days and declined thereafter(P<0.05).The concentration of β-hydroxybutyrate(BHBA)increased from 60 to 120 days,finally reaching the highest at 120 days of age(P<0.05).The concentration of immunoglobulin G(IgG),IgM,IgA,interleukin-1β(IL-1β),IL-6,IL-12,tumor necrosis factor-α(TNF-α),lipopolysaccharide(LPS),and d-lactic acid(DLA)had the highest value at 30 days of age(P<0.05).Compared to other age groups,the concentration of IL-17 was highest at 30 days of age(P<0.05).Meanwhile,antioxidant indicators of serum superoxide dismutase(SOD)and total antioxidant capacity(T-AOC)increased(P<0.05)from 30 days to 60 days and then decreased(P<0.05)thereafter,and the quadratic effect was significant(P<0.05).Compared to other age groups,the concentration of serum glutathione peroxidase(GsH-Px)was lower(P<0.05)at 120 days of age.The concentration of malondialdehyde(MDA)decreased(P<0.05)linearly with increasing age.Rumen ammonia N concentration was highest(P<0.05)at 30 days of age.The concentration of microbial crude protein(MCP)increased from birth to 10 days of age and became relatively stable thereafter(P<0.05).Except for valerate which appeared at 10 days of age,other volatile fatty acids(total VFA,acetate,propionate,butyrate,isobutyrate,and isovalerate)appeared at 3 days of age,and the concentration of all volatile fatty acids reached the highest(P<0.05)at 60 days of age.Thereafter,the growth performance,rumen fermentation,and serum parameters were changed with the increased age of lambs and became stable.Experimental 2 was to investigate the dynamic changes of bacterial communities in the gastrointestinal tract of growing lambs.Our study used 10 newborn lambs(Hu sheep breed,female,singletons)using 16S-rRNA amplicon sequencing data and studying the rumen and rectum bacterial communities at 0,3,10,20,30,45,60,90,and 120 days of age in lambs.The results demonstrated that the rumen and rectum bacterial communities were all affected(P<0.05)by the age of lambs.Based on the Bray-Curtis distance within the age groups of the rumen microbiota,the similarity increased(P<0.05)sharply after the lambs were weaned at 60 days of age.The similarity between the samples collected from birth to 90 days of age and those collected at 120 days of age,increased after 20 days,reaching a maximum at 90 days vs.120 days(P<0.05).The analysis of the rectum indicated that similarity within age groups of fecal microbiota was lower in the preweaning period and increased sharply(P<0.05)after weaning at 60 days.The similarity between the samples collected from birth to 90 days of age and those collected at 120 days of age,increased(P<0.05)sharply after 30 days of age.Some age-associated changes in the microbial genera were correlated with changes in the concentrations of volatile fatty acids and the levels of microbial crude protein in the rumen,including positive correlations(P<0.05)between main volatile fatty acids and the genera of Prevotella 1,Lachnospiraceae NK3A20 group,Ruminococcus gauvreauii group,Ruminococcaceae UCG-014,and Ruminococcus 2.Some age-associated changes in microbial genera were correlated with the changes in concentrations of immune indicators,including negative(P<0.05)correlations between the relative abundance of Lachnospiraceae UCG-010,Eubacterium coprostanoligenes group,Ruminococcaceae UCG-005,Ruminococcaceae UCG-009,Ruminococcaceae UCG-013,Ruminiclostridium 6,Ruminococcaceae UCG-008,and Oscillibacter with serum concentrations of LPS,DLA,IgA,IgM,IgG,IL-1β,IL-6,IL-12,IL-17,and TNF-α,and the relative abundance of these genera increased from 45 days of age.Our study analyzed the colonization progress of rumen and rectum bacterial communities from birth to 120 days of age in lambs,meanwhile the relationships between bacteria,rumen fermentation,and serum parameters,thus there might be a critical window that provides an opportunity for potential manipulation of the bacterial ecosystems.Experimental 3 was conducted to study the dynamic changes of rumen and rectum fungal communities of lambs from birth to 120 days of age.The experimental animals and design were the same as experimental 2.This study investigated fungal community dynamics in the rumen and rectum of lambs from birth to 120 days of age by using IT1S rDNA sequencing technology together with the RandomForest approach to determine age-related changes in the fungal ecology.The results illustrated that the rumen and rectum fungal community composition,diversity,and abundance altered(P<0.05)with the increasing age of the lambs.Two phyla,Ascomycota and Basidiomycota,dominated the samples.Similarity within age groups of the rumen fungi increased sharply after 45 days of age,while the similarity increased(P<0.05)significantly after 60 days of age in the rectum.The age-related genera,Acremonium,Microascus,Valsonectria,Myrmecridium,Scopulariopsis,Myrothecium,Saccharomyces,and Stephanonectria,were presented in both ruminal and rectal communities,and their changes in relative abundance were consistent at both sites,demonstrating that these genera may play a vital role in the development of lambs,and indicating that the microbial community of foregut may influence the hindgut.Our research suggests that the succession process of the fungi can be divided into 3 phases:colonization(0～10 days of age),transition(10～45 days of age),and a relatively stable period of maturation(45～120 days of age).Our findings demonstrate that both the age of lambs and the gastrointestinal tract region can affect the composition of these fungal communities,and this provides new insight and directions for future studies in this research area.The objective of experimental 4 was to investigate whether rumen fluid transplantation(RT)can reduce the negative influence of weaning.Hence,in this study,thirty-eight pre-weaning lambs(Hu sheep breed,female)were randomly assigned to one of three treatment groups:control lambs(CON,n=14)received 25 ml of normal saline solution,and lambs in two RT groups received 25 ml of rumen fluid either from 3-month-old lambs(LT,n=12)or from one-year-old ewes(AT,n=12).The effects on their growth performance,nutrient digestibility,some blood parameters,and gastrointestinal tract microbiota were monitored.There were differences(P<0.05)in rumen bacterial composition between the groups at weaning,at 3 months,and at 1 year.Rumen fluid transplantation decreased(P<0.05)average daily feed intake,average daily gain in live weight,and apparent digestibility of ether extract in the LT group,and it decreased(P<0.05)apparent digestibility of NDF and ADF in the AT group.Rumen fluid transplantation also increased(P<0.05)concentrations of serum immunoglobulin A in the AT group and increased(P<0.05)serum concentrations of interleukin-6,interferon alpha,and d-lactic acid in both LT and AT groups.Bacterial α-diversity in the rumen and rectum was not affected by RT(P>0.05),but a bacterial community change was observed after RT,and the abundance of some dominant bacteria in both rumen and rectum changed after RT(P<0.05).Analysis of correlations between the parameters indicated that the altered gastrointestinal microbiota and accelerated maturity of rumen micro-organisms induced by RT caused some impairment of gastrointestinal integrity and immunity,which led to decreased feed intake,reduced feed digestibility,and lower growth performance of the weaned lambs.In conclusion,rumen fluid transplantation altered the gastrointestinal microbiota causing adverse effects on feed intake,feed digestibility,and growth performance of the weaned lambs.In conclusion,our research found that the growth performance,blood parameters,and rumen fermentation of lambs gradually stabilized with the increase of age.The colonization process of bacterial and fungal communities in the rumen and rectum of lambs from birth to 120 days of age was systematically studied.It was found that both the gastrointestinal tract region and the age of lambs affected the composition of these microbial communities,and the key microbial taxa in the maturation process of the rumen and rectum community of lambs were determined,providing a theoretical foundation for improving the growth performance of lambs.The growth experiment found that the weaned lambs had a lower average daily gain.The rumen fluid transplantation influenced the rumen microbial maturity of weaned lambs,but the adverse effects of rumen fluid transplantation were also found,which provided new insight for the application of this technology in the future. |
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