The aim of the diploma thesis was to determine the content and composition of toxic pyrrolizindine alkaloids (PA) in marsh ragwort (Senecio aquaticus) to be able to estimate whether and in which amounts Senecio aquaticus containing hay can be fed to animals. The examined Senecio aquaticus came from the Waldviertel in Lower Austria where the proportion of this plant in the meadows is partially very high and poisoning of horses and cattle occurred during the last years. The plants were mowed at several different dates in order to find out whether the composition and the content in PA, varied during a vegetation period.
Moreover, in a population the variability in the alkaloid content from 30 individual plants was examined.
The shoot of the ragwort was dried and ground. After extraction and clean up, the alkaloid content of the plants was determined by means of GC/MS. The PAs senecionine, seneciphylline, integerrimine, Z-erucifoline and acetyl-erucifoline could be determined. The main alkaloids were senecionine and erucifoline. While the senecionine concentration rose until August and sank afterwards, the erucifoline concentration decreased during the vegetation period.
The main alkaloid extracted from the population of 30 individual plants was erucifoline. Significant variations in the concentration were noticeable. In some individuals erucifoline could not be found, whereas in others it was up to four times of the average erucifoline content of the population.
The proportion of Senecio aquaticus and therefore the PA content of the hay were highest during the blossom and seminal production in July, August and September. The lowest alkaloid content was fond in the hay which was cut at the beginning of June, when the marsh ragwort is still in the rosette stage and also late in autumn when the ragwort began to decay. Hence, a use of the first cut can be taken into consideration if the proportion of marsh ragwort in the meadow is low. One cut in late autumn is not a good option, because the ragwort seeds have already fallen out, further spreading of S. aquaticus is promoted and the nutritive value of the hay is low.
The extracted PAs are cyclic diesters, the most toxic group of PAs. Horse are more sensitive to cyclic diester-intoxications than cattle and small ruminants, but further research would be necessary to determine the toxicity of Senecio aquaticus for single species more precisely.