In vitro rumen fermentation of feed substrates added with chestnut tannins or an extract from Stevia rebaudiana Bertoni

Rumen fermentation parameters and microbiota were evaluated in 3 in vitro rumen fermentation experiments after addition of chestnut tannins(CWT)or an extract from Stevia rebaudiana Bertoni(SB)to substrates.A control(CTR)substrate was fermented alone or added with 1.5%of CWT or SB extracts in a batch culture system(Exp.1,fermentation in 500 mL for 24 h)and in a subsequent continuous culture system(Exp.2,fermentation in 2 L bottles for 9 d).Experiment 3 used the fermentation system of Exp.1 and tested 7 doses of each extract added to CTR(additions of 0.2%,0.4%,0.6%,0.8%,1.0%,1.2%and 1.4%for48 h).The addition of CWT lowered(P<0.01)the in vitro rumen ammonia concentration in all experiments and reduced the protozoa counts in Exp.1(P<0.05).In contrast,the SB extract did not modify the ammonia concentrations,but significantly lowered the protozoa counts in all 3 experiments(reduction of 47%and 20%in Exp.1 and 2,P<0.05;and a quadratic reduction in Exp.3,R^2=0.63,P<0.01).Neither extract affected the fermentation in terms of gas production(Exp.1 and 3)nor volatile fatty acids(VFA)yield(Exp.1 and 2),if we exclude a reduction at the highest CWT concentration in Exp.3.Changes in VFA profile were induced by CWT and were limited to reductions in the iso-valerate(P<0.01,in Exp.2)and iso-butyrate levels(P<0.01,Exp.2).The CWT increased the abundance of Prevotella ruminicola and Selenomonas ruminantium and decreased that of Ruminobacter amylophilus(P<0.01,P<0.05 and P<0.05,respectively).The SB extract increased the relative abundance of Treponema saccarophylum(P<0.05).Both of the studied substances had an impact on rumen metabolism,with SB reducing protozoa counts and CWT lowering the rumen ammonia concentration.The effects of both extracts on the rumen were appreciable at low dietary doses,and the negative impacts on fermentation were limited to the reduction in protein degradation with the addition of CWT.

Evaluation of dietary addition of 2 essential oils from Achillea moschata,or their components (bornyl acetate,camphor,and eucalyptol) on in vitro ruminal fermentation and microbial community composition

This study investigated the effects of 2 Achillea moschata essential oils extracted from plants collected in 2 different valleys of the Italian Alps and 3 pure compounds of oils—bornyl acetate(BOR),camphor(CAM),and eucalyptol(EUCA)—on in vitro ruminal fermentation and microbiota.An in vitro batch fermentation experiment(Exp.1)tested the addition of all of the substances(2 essential oils and 3 compounds)in fermentation bottles(120 mL)at 48 h of incubation,whereas a subsequent in vitro continuous culture experiment(Exp.2)evaluated the pure compounds added to the fermenters(2 L)for a longer incubation period(9 d).In both experiments,total mixed rations were incubated with the additives,and samples without additives were included as the control(CTR).Each treatment was tested in duplicate and was repeated in 3 and 2 fermentation runs in Exp.1 and 2,respectively.Gas production(GP)in Exp.1 was similar for all of the treatments,and short chain volatile fatty acid(SCFA)production was similar in both experiments except for a decrease of SCFA produced(P=0.029)due to EUCA addition in Exp.2.Compared to CTR,BOR and CAM reduced the valerate proportion(P=0.04)in Exp.1,and increased(P<0.01)the acetate proportion in Exp.2.All treatments increased(P<0.01)total protozoa counts(+36.7%and+48.4%compared to CTR on average for Exp.1 and 2,respectively).In Exp.1,all of the treatments lowered the Bacteroidetes and Firmicutes and increased the Proteobacteria relative abundances(P<0.05),whereas in Exp.2,the EUCA addition increased(P=0.012)the Ruminococcus.In Exp.1,methane(CH4)as a proportion of the GP was lowered(P=0.004)by the addition of CAM and EUCA compared to CTR,whereas in Exp.2,EUCA reduced the amount of stoichiometrically calculated CH4 compared to CTR.Overall,essential oils extracted from A.moschata and the pure compounds did not depress in vitro rumen fermentation,except for EUCA in Exp.2.In both experiments,an increase of the protozoal population occurred for all the additives.