| In practical beef production,due to lack of high-quality roughage,producers have to feed beef cattle with high-concentrate diet in order to gain fast finishing However,longtime of feeding this kind of diet will lead to metabolic disorders of rumen,and subsequently induce subacute ruminal acidosis(SARA).Bacteria in the rumen which are low-pH intolerance will massively dead and release lipopolysaccharide(LPS)into blood,thus to arouse body inflammation.Prebiotics,using as a regulator of gastrointestinal health,have been proved available on many animals.Among these prebiotics,inulin is considered to be the most regulative one Studies indicated that inulin could act as substrate of gut beneficial bacteria like Lactobacillus and Bifidobacterium,in the meantime,suppress the growth of harmful bacteria like Escherichia coli,to finally optimize the gastrointestinal microbiota.In particular,inulin may reduce the side effects of high-concentrate diet feeding by regulating rumen fermentation and microbiota.Thus,the objective of the present study was to evaluate the effects of dietary inulin supplementation on rumen fermentation and bacterial microbiota,inflammatory response and growth performance in finishing beef steers fed high or low-concentrate diet,aims to provide experimental basis for the application of inulin in beef production24 healthy Simmental × Luxi crossbred steers with similar body conditions and initial body weight of 319 ± 8.4 kg were selected to a 2 × 2 treatment with 2 diet types and 2 inulin levels,the diet types included a low-concentrate diet(LCD;concentrate roughage=40:60)and a high-concentrate diet(HCD;concentrate:roughage=60:40),inulin was supplemented into the diets at 0 or 2%(wt/wt).The experiment last for 42 days after a 7-days adjustment period,cattle were fed at 0700 and 1700 daily with free access to water.Fecal,ruminal fluid and blood samples were collected at the end of experiment for measuring growth performance,nutrient apparent digestibility,ruminal microbiota and inflammatory responsesResult showed:(1)compared with LCD,HCD has significantly higher final body weight,average daily gain(ADG)and average daily feed intake(P<0.05),also with a lower feed conversion ratio(P<0.001);inulin supplementation increased the final body weight and ADG(P<0.05),decreased the feed conversion ratio(P=0.005).(2)Inulin supplementation increased the apparent digestibility of crude protein and ether extract.Inulin supplementation into the HCD lower the digestibility of neutral detergent fiber and total phosphorus(TP,P<0.05),however inulin supplementation into LCD had no effect on either of the indices(P>0.05).(3)HCD decreased ruminal pH value and the concentration of acetate(P<0.05),increased the concentrations of propionate,iso-butyrate and valerate(P<0.05),compared with LCD;inulin supplementation significantly decreased the ruminal pH value(P=0.009),increased the concentrations of propionate,butyrate and iso-butyrate in the rumen(P<0.05).(4)HCD decreased the operational taxonomic units(OTUs)of ruminal bacteria(P=0.02),also decreased the Shannon and Simpson indices of alpha indices(P<0.05);the effect of inulin supplementation into LCD and HCD have different results,inulin supplementation into HCD increased the bacteria OTUs(P=0.02)and increased all of the alpha indices including:ACE,Chao1,Shannon and Simpson indices(P<0.05);inulin supplementation into LCD decreased the OTUs(P<0.05),while decreased Shannon index,inulin supplementation have no effect on the other 3 indices(P<0.05).(5)At the phylum level,HCD increased the relative abundance of Firmicutes and Actinobacteria(P<0.05),decreased the relative abundance of Bacteroidetes(P<0.05);at the genus level,HCD increased the relative abundance of Sharpea,Succiniclasticum and Butyrivibrio(P<0.05),decreased the relative abundance of Prevotella(P<0.05);inulin supplementation increased the relative abundance of Bacteroidetes(P<0.001),decreased the relative abundance of Firmicutes and Actinobacteria(P<0.05).(6)HCD increased the LPS concentrations in ruminal fluid and blood(P<0.001);inulin supplementation into HCD increased ruminal LPS concentration(P<0.05),but didn't affect LPS concentration in blood(P>0.1).(7)HCD increased the inflammatory cytokines in blood including interleukin(IL)1?,IL-6 and IL-8,also increased tumor necrosis factor-?,in the meantime,HCD increased all acute phase proteins including lipopolysaccharide-binding protein,haptoglobin,serum amyloid A and C reactive protein(P<0.05);inulin supplementation had no effect on either acute phase protein nor inflammatory cytokines(P>0.05).(8)inulin supplementation increased ruminal LPS concentration(P=0.014),but had no effect on plasma LPS concentration(P=0.158)To sum up,dietary supplementation of inulin in finishing beef steers fed high or low-concentrate diet,can both increase final body weight,decrease feed conversion ratio;through enhancing richness and diversity of ruminal bacteria,inulin supplementation into HCD can optimize the composition and proportion of ruminal microbiota;inulin supplementation into LCD can regulate ruminal microbiota,increase the proportion of propionate/acetate.However,dietary supplementation of inulin failed to alleviate inflammatory response of finishing steers which feed HCD for a longtime. |
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