Differential effects of monensin and a blend of essential oils on rumen microbiota composition of transition dairy cows

Abstract

In response to oral application, monensin alters the rumen microbiota, increasing ruminal propionate production and energy availability in the animal. Data from different studies indicate that the susceptibility of rumen bacteria to monensin is mainly cell-wall dependent but tracing its activity to specific microbial groups has been challenging. Several studies have shown a similar effect for essential oils but results are inconsistent. To investigate the influence of monensin and a blend of essential oils (BEO, containing thymol, guaiacol, eugenol, vanillin, salicylaldehyde, and limonene) on the rumen microbiome, rumen liquid samples were collected orally on d 56 postpartum from cows that had either received a monensin controlled-release capsule 3 wk antepartum, a diet containing a BEO from 3 wk antepartum onward, or a control diet (n = 12). The samples were analyzed for pH, volatile fatty acid, ammonia, and lipopolysaccharide concentrations and protozoal counts. A 16S rRNA gene fingerprinting analysis (PCR-single-strand conformation polymorphism) and sequencing revealed that the BEO treatment had no effect on the rumen microbiota, whereas monensin decreased bacterial diversity. Twenty-three bacterial species-level operational taxonomic units were identified for which monensin caused a significant decrease in their relative abundance, all belonging to the phyla Bacteroidetes (uncultured BS11 gut group and BS9 gut group) and Firmicutes (Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae). Ten bacterial operational taxonomic units belonging to the phyla Actinobacteria (Coriobacteriaceae), Bacteroidetes (Prevotella), Cyanobacteria (SHA-109), and Firmicutes (Lachnospiraceae and Ruminococcaceae) increased in relative abundance due to the monensin treatment. These results confirm the hypothesis that varying effects depending on cell-wall constitution and thickness might apply for monensin sensitivity rather than a clear-cut difference between gram-negative and gram-positive bacteria. No effect of monensin on the archaea population was observed, confirming the assumption that reported inhibition of methanogenesis is most likely caused through a decrease in substrate availability, rather than by a direct effect on the methanogens. The data support the hypothesis that the observed increase in ruminal molar propionate proportions due to monensin may be caused by a decrease in abundance of non-producers and moderate producers of propionate and an increase in abundance of succinate and propionate producers.

Monensin and Nisin Affect Rumen Fermentation and Microbiota Differently In Vitro

“…Supporting this notion, the present study also showed a decrease in H 2 -producing microorganisms, including protozoa, fungi, and Gram-positive taxa of Firmicutes , to which the primary ruminal H 2 -producing bacteria belong. Different with our in vitro result, one recently published in vivo study showed no effect of monensin on archaea population (Schären et al, 2017). Undoubtedly, their results further confirmed that the inhibition of methanogenesis by monensin is most likely caused by a decrease in substrate availability, rather than by direct inhibition to methanogens.…”

“…Therefore, the greatly increased relative abundance of Succinivibrio (>11.38%) and Selenomonas (>2.45%) in the MON and the nisin treatments probably contributed to increased propionate via the succinate pathway. Similar to our results, an in vivo study also found an increase in ruminal propionate proportions after monensin addition, which was caused by an increase in abundance of succinate and propionate producers and a decrease in non-producers (Schären et al, 2017). In addition, the acrylate pathway is also an important propionate-producing pathway in the rumen, in which lactate-producing bacteria such as Streptococcus bovis play a key regulatory role (Jeyanathan et al, 2014).…”

Metagenomic characterization of the effect of feed additives on the gut microbiome and antibiotic resistome of feedlot cattle

“…In the rumen, use of antibiotic feed additives was inversely associated with species diversity and richness as indicated by lower Chao1, ShannonH, and inverse Simpson indices for AB steers. Previous research also had shown that monensin decreased rumen bacterial diversity both in vitro and in vivo 39,40 . Contrary to the findings in the rumen, the microbial population in colon and cecum samples had similar diversity for both treatment groups.…”

Alterations in the Rumen Liquid-, Particle- and Epithelium-Associated Microbiota of Dairy Cows during the Transition from a Silage- and Concentrate-Based Ration to Pasture in Spring

“…Further, similar to our results de Menezes et al (2011) have shown a higher species diversity in the LAAB compared to the PAAB, whereas the results of Kong et al (2010), Pitta et al (2010), and Sadet et al (2007) show the opposite. We suggest that these observed differences among studies can be ascribed to differences in ration composition (Henderson et al, 2015), time the animals received the ration prior to sampling (Hackmann, 2015), number of animals sampled (Weimer, 2015), sample collection (Li et al, 2009), microorganism and DNA isolation (Henderson et al, 2013), microbiota analysis method (DNA fingerprinting vs. amplicon sequencing, Sadet et al, 2007), sequencing platform and depth (Klindworth et al, 2013, also discussed in Schären et al, 2017). …”

“…The separation of the liquid-associated microbes from feed particles and the subsequent DNA extraction have been described by Meibaum et al (2012) and Schären et al (2017) (exact protocol). Briefly, several centrifugation steps were performed (once 5 min at 600 g (4°C) to remove feed particles and debris, and four times during 20 min at 27,000 g (4°C); between each centrifugation step the pellet was re-suspended in 40 mL 0.9% NaCl) and the concentrated samples were liquid shock frozen under the form of droplets for storage at −80°C.…”