Effect of monensin feeding and withdrawal on populations of individual bacterial species in the rumen of lactating dairy cows fed high-starch rations

Abstract

Real-time polymerase chain reaction (PCR) was used to quantify 16 procaryotic taxa in the rumina of two lactating dairy cows following supply and subsequent withdrawal of the feed additive monensin (13.9 mg/kg of diet dry matter) in a high-starch, silage-based ration. PCR was conducted on DNA from rumen samples collected 6 h post feeding on two successive days before monensin supplementation, after 30 days of monensin supplementation, and at six weekly intervals after monensin withdrawal. Mean values of relative population size (RPS, the percent of bacterial 16S rRNA copy number) for genus Prevotella increased (P < 0.05) from 41.8% without monensin to 49.2% with monensin and declined to 42.5% after monensin withdrawal. Mean RPS values for two biohydrogenating species (Megasphaera elsdenii and Butyrivibrio fibrisolvens) were low (<0.4%) and declined several-fold in response to monensin. Mean RPS values for the biohydrogenating species Eubacterium ruminantium, four cellulolytic species, four starch- or dextrin-fermenting species, and Domain Archaea were not altered (P > 0.10) upon monensin feeding or withdrawal. The data suggest that monensin in high-starch diets does not suppress populations of classical ruminal Gram-positive bacteria or the availability of H2, though it may affect bacteria involved in biohydrogenation of lipids that regulate bovine mammary lipogenesis.

Effects of Dietary Supplementation with Hainanmycin on Protein Degradation and Populations of Ammonia-producing Bacteria &lt;italic&gt;In vitro&lt;/italic&gt;

“…Treatment H10 and H100 reduced relative population sizes (RPS) of B. fibrisolvens during incubation, which may result from the fact that B. fibrisolvens as gram-positive bacteria is sensitive to ionophores. The RPS of P. ruminicola was increased in H10 and H100, which was similar to the results of Weimer et al (2008) who observed that dietary supplementation of monensin increased relative ruminal population sizes of P. ruminicola during rumen fermentation of lactating dairy cows. P. ruminicola is also the predominant species of proteolytic bacterium in the rumen (van Gylswyk, 1990).…”

Investigation of ruminal bacterial diversity in dairy cattle fed supplementary monensin alone and in combination with fat, using pyrosequencing analysis

“…Pure culture studies have shown that monensin is more inhibitory to Gram-positive bacteria than Gram-negative bacteria (Haney and Hoehn 1967;Liu 1982;Petzel and Hartman 1985), and monensin was thought to modulate ruminal bacterial communities through its selective inhibitory effect on Gram-positive bacteria (Callaway et al 2003). However, some in vivo studies using rrs-based techniques showed that Gram-positive bacterial populations are not significantly affected by monensin (Stahl et al 1988;Weimer et al 2008). In addition, some in vivo studies showed that acetate:propionate ratio is not altered by monensin (Firkins et al 2008;Oelker et al 2009;Mathew et al 2011).…”

Effects of Methanogenic Inhibitors on Methane Production and Abundances of Methanogens and Cellulolytic Bacteria in In Vitro Ruminal Cultures

“…To mitigate the negative impact on climate change and to improve feed efficiency, numerous strategies for reducing methane emission from ruminant livestock have been tested. Plant extracts (7,9), vaccines (28), ionophores (27), and dietary strategies (21) have been evaluated for their efficacy in reducing ruminal methane emission. However, only monensin has been used in animal-feeding operations, and it typically achieves only transient reductions in methane production (12).…”