| Popis: |
Prežvekovalci so pomemben vir emisij metana v ozračje, kjer ima ta negativen vpliv na globalno segrevanje. Preverjen in učinkovit način zmanjšanja emisij metana predstavljajo antibiotični krmni dodatki, katerih uporaba je v Evropski skupnosti od 1.1.2006 prepovedana, zato iščemo alternativo, med drugim v izvlečkih nekaterih rastlin. V raziskavi smo uporabili šaržni anaerobni bioreaktorski sistem, s katerim smo simulirali razmere v vampu ovac in tako in vitro preučevali in primerjali vpliv izvlečkov česna, hmelja in kostanjevih taninov na proizvodnjo plinov (celokupno, CO2, CH4 in H2) in kratkoverižnih maščobnih kislin (KMK). Z molekularnimi metodami (TRFLP) in bioinformacijsko analizo pa smo preučevali vpliv teh učinkovin na sestavo bakterijskega in arhejskega dela vampovega mikrobioma. Vpliv rastlinskih izvlečkov smo primerjali tudi z vplivom ionofornega antibiotika monenzina. Ugotovili smo, da imajo dodatki izbranih rastlinskih izvlečkov v večini statistično značilen učinek na celotno proizvodnjo plina kot tudi proizvodnjo metana. Največji učinek sta imela dodatek česnovega olja in beta kislin iz hmelja, ki sta bila ob dodatku višje koncentracije celo učinkovitejša od dodatka monezina. Dodatek monenzina, česnovega olja in beta kislin iz hmelja je povzročil kopičenje vodika namesto metana, domnevno zaradi zaviranja procesa metanogeneze. Analiza kratkoverižnih maščobnih kislin je pokazala, da je dodatek izbranih rastlinskih izvlečkov povzročil zmanjšanje koncentracije le teh, z izjemo dialil disulfida (DADS), kjer se je celokupna koncentracija KMK povečala. DADS v primerjavi s pozitivno kontrolo ni spremenil razmerja med ocetno in propionsko kislino, medtem ko so ga druge učinkovine zmanjšale (z izjemo alfa kislin iz hmelja). Z analizo profilov TRFLP bakterijskih in arhejskih delov mikrobiomov smo ugotovili, da je dodatek vsake učinkovine specifično vplival na profil mikrobioma, pri čemer so med njimi opazne razlike. Analiza profilov bakterijskega dela mikrobiomov je pokazala veliko podobnost mikrobiomov iz vzorcev z dodanimi rastlinskimi učinkovinami in vzorcev pozitivnih kontrol, medtem ko je dodatek monenzina bakterijski del mikrobiomov močno spremenil. Drugačna razporeditev je značilna za arhejski del mikrobiomov, na katere je najbolj vplival dodatek dialil disulfida. Ruminants are major source of methane emissions to the atmosphere, which negatively impacts global warming. A proven and effective means of reducing methane emissions are antibiotic feed additives, the use of which has been banned in the European Community, so we are looking for and alternative, which includes extracts of certain plants. In this research we used anaerobic batch bioreactor system to simulate the conditions in the rumen of sheep, and thus studied and compared in vitro the influence of extracts of garlic, hops, and chesnut tannin on the production of gases (total, CO2, CH4 and H2) and short-chain fatty acids (SCFA). Using molecular methods (TRFLP) and bioinformatic analyses, we studied the influence on these compounds on the composition of the bacterial and archaeal part of the rumen microbiome. The effect of the plant extracts was also compared with the effect of the antibiotic monensin (MON). We found that the addition of selected plant extracts had a statistically significant effect on total gas production as well as methane production in most cases. The greatest effect was obtained by the addition of garlic oil and beta acids from hops, which were even more effective than the addition of MON at higher concentrations. The addition of MON, garlic oil, and beta acids resulted in the production of hydrogen instead of methane, probably due to the inhibition of methanogenesis. Analysis of SCFA showed, that the addition of selected plant extracts led to a decrease in the production of these fatty acids, with the exception of diallyl disulfide (DADS), which increased their production. DADS did not change the ratio of acetic to propionic acid compared with the positive control, where as the other active ingredients decreased it (with the exception of alpha acids from hops). When analysing the profiles of the bacterial and archaeal parts of the microbiome, we found that the addition of each active ingredient had a specific effect on the profile of the microbiomes, with clear differences between them. The analysis of the bacterial part of the microbiomes showed a great similarity between the microbiomes of the samples with added plant extracts and the positive control samples, while the addition of monensin strongly changed that part of microbiomes. A different distribution is characteristic for the achaeal part of the microbiomes, which was most affected by the addition of DADS. |
