Study on Toxic Substances in Astragalus adsurgens Infected with Alternaria gansuense

Yellow stunt and root rot causes premature degradation of Astragalus adsurgens grasslands in China. However, the etiological factors underlying livestock poisoning following the ingestion of diseased plants remain elusive. The present study aimed to comprehensively characterize the alterations in toxic substances such as swainsonine and trace element profiles in A. adsurgens after infection with Alternaria gansuense, thereby elucidating the underlying mechanisms of livestock toxicity. Using ELISA and regression analyses, we found that diseased plants had higher selenium levels than the healthy ones, with varietal differences. Selenium in the Zahua variety was higher in healthy plants, while diseased plants of the Henan variety had the highest levels. Moreover, the diseased plants demonstrated decreased levels of iron, zinc, sodium, and magnesium, while manganese and calcium concentrations remained unchanged. Swainsonine was detected in both the healthy and infected specimens of Zhongsha No.1 and Henan varieties, with a marked post-infection increase. In conclusion, swainsonine is the primary toxin causing livestock poisoning, and it is unlikely that soil-accumulated selenium poisons animals. However, potential correlations might exist among the contents of selenium, sodium, and swainsonine. We recommend the cautious use of diseased A. adsurgens as livestock feed.