Authors: Ohlsen Susanne, Ganter Martin, Wohlsein Peter, Reckels Bernd, Huckauf Aiko, Lenzewski Nikola, Aboling Sabine
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Pyrrolizidine alkaloids in common ragwort pose a well-documented toxicity risk to horses and cattle, yet field evidence on whether grazing animals can safely ingest this plant whilst actively reducing pasture populations remains limited. Researchers monitored sheep grazing a ragwort-dominated pasture over two years at 12 head per hectare, measuring voluntary ragwort intake, correlations between nutritional content and grazing behaviour, and changes in botanical composition and flowering patterns across regular six-weekly surveys. Sheep consumed between 1.2–4.9 kg of ragwort daily in 2020 and 1.0–2.2 kg in 2021 without adverse health effects, with intake strongly linked to sugar content in the plant material (correlation coefficients 0.94–0.95); concurrently, ragwort's proportion of pasture biomass declined from 26.3% to 18.8% whilst other herbs increased from 23.3% to 36.5%, and flower production doubled. These findings suggest that targeted sheep grazing offers a practical biological control option for ragwort management, delivering simultaneous benefits for animal welfare and conservation by exploiting sheep's demonstrated tolerance and palatability preference for this otherwise problematic species—a consideration worth exploring for mixed grazing enterprises seeking non-chemical weed control strategies.
Read the full abstract on PubMed
Practical Takeaways
- •Sheep demonstrate natural tolerance to ragwort toxins and actively prefer the plant when sugar content is high, making them useful for biological weed control on contaminated pastures
- •Field observations confirm sheep can safely graze ragwort-rich pastures at 12 sheep/hectare without health consequences, supporting integrated grazing management for conservation
- •While findings are for sheep, equine practitioners should note that horses remain at high risk from ragwort and should not graze pastures managed with sheep for ragwort control
Key Findings
- •Sheep continuously ingested 1.0-4.9 kg ragwort per individual per day over two years without adverse health effects
- •Ragwort sugar content correlated strongly with sheep intake (r = 0.94-0.95), suggesting palatability preference
- •Grazing reduced ragwort yield proportion from 26.3% to 18.8% while increasing other herbs from 23.3% to 36.5%
- •Sheep grazing effectively controlled ragwort populations while doubling flower production of competing plants