Investigations on the possible impact of a glyphosate-containing herbicide on ruminal metabolism and bacteriain vitroby means of the ‘Rumen Simulation Technique’

Abstract

Aims: This study was performed in a well-established in vitro model to investigate whether the application of a glyphosate-containing herbicide might affect the bacterial communities and some biochemical parameters in a cow's rumen. Methods and Results: The test item was applied in two concentrations (high and low) for 5 days. In a second trial, fermentation vessels were inoculated with Clostridium sporogenes before the high dose was applied. Effluents were analysed by biochemical, microbiological and genetic methods. A marginal increase in short-chain fatty acid production and a reduction in NH 3 -N were observed. There were minor and rather equivocal changes in the composition of ruminal bacteria but no indications of a shift towards a more frequent abundance of pathogenic Clostridia species. Clostridium sporogenes counts declined consistently. Conclusions: No adverse effects of the herbicide on ruminal metabolism or composition of the bacterial communities could be detected. In particular, there was no evidence of a suspected stimulation of Clostridia growth. Significance and Impact of the Study: Antibiotic activity of glyphosate resulting in microbial imbalances has been postulated. In this exploratory study, however, intraruminal application of concentrations reflecting potential exposure of dairy cows or beef cattle did not exhibit significant effects on bacterial communities in a complex in vitro system. The low number of replicates (n = 3/dose) may leave some uncertainty.

Evaluation of the impact of glyphosate and its residues in feed on animal health

“…With regard to a new disease in cattle mainly occurring in the northern parts of Germany and of unknown aetiology, high growth of Clostridium botulinum in the rumen and formation of Clostridium neurotoxins due to possible glyphosate‐induced microbial imbalance have been hypothesised. In vitro data from the ‘Rumen Simulation Technique’ (Riede et al., ) showed that, in general, microbial communities of the rumen were not affected by the administration of glyphosate acid, and the herbicide had no effect on the growth of Clostridium sporogenes (surrogate for Clostridium botulinum ) up to a dose level of 292 ppm in the diet (dry matter), as recalculated by EFSA considering comments provided during the written procedure on the draft scientific report and taking into account the actual analytical determination of the high dose administered. It was also noted that this exploratory study had limitations (e.g.…”

Facts and Fallacies in the Debate on Glyphosate Toxicity

“…At this stage, it is currently not clear whether glyphosate has an effect on the mammalian gut microbiome, especially at environmentally relevant levels of exposure. Nonetheless, some studies have shown that glyphosate and glyphosate-based herbicides such as Roundup can selectively affect bacterial populations in vitro ( 22 ) while others have reported no adverse effects ( 23 ). Given these discrepancies additional research is clearly needed to ascertain whether glyphosate-based herbicides at environmentally relevant levels of ingestion can result in disturbances in the gut microbiome of human and animal populations with negative health implications.…”

Effects of drought‐stressed temperate forage legumes on the degradation and the rumen microbial community in vitro

“…Therefore, of the air‐dry substrate 6.66 g was weighed into nylon bags of 50 µm pore size. The composition of the buffer solution is described in detail by Riede et al (). Buffer solution was infused at a rate of 375 ml/day into each fermentation vessel.…”