In vitro biodegradation of cyanotoxins in the rumen fluid of cattle

Abstract

Background: In countries around the Baltic Sea grazing ruminants have access to and drink, surface water from lakes, rivers and in several coastal regions. The water quality of these naturally occurring reservoirs affects performance and health of livestock. In the Baltic Sea both microcystin (MC) and nodularin (NOD) occurs as cyclic peptides and have hepatotoxic effects. Although cattle obviously have died after consuming contaminated water very little information is available as to how susceptible ruminants are to the toxins produced by cyanobacteria. The critical question as to whether the rumen microflora might constitute a protective shield is unresolved. For this reason our aim is to investigate a possible degradation rate of these toxins in rumen.

Results: The ability of rumen microorganisms to degrade certain important cyanotoxins (MC-LR, YR, RR and NOD) was studied in vitro by incubating with rumen fluid at three different concentrations (0.05, 0.5 and 5 μg/mL) for 3 h. The degradation efficiencies were determined by LC-MS (ESI) positive mode. Degradation was observed in the following order MC-RR 36%, NOD 35%, MC-RR 25% and MC-LR 8.9% at lower concentrations within 3 h. However, average degradation was observed at concentration of 0.5 μg/mL. No degradation was observed in higher concentrations for entire 3 h. The present results reveal that the degradation was both dose and time dependent.

Conclusions: In conclusion the present results suggest that the rumen microbial flora may protect ruminants from being intoxicated by Cyanotoxins.

Figure 1

Dose dependent degradation of cyanotoxins (A) 0.5 μg/mL and (B) 0.05 μg/mL.

Figure 2

Time dependent degradation of cyanotoxins by rumen microbial flora within 3 h of incubation (A) MC-YR (B) NOD (C) MC-RR (D) MC-LR.