Fructan content in pasture grasses
Authors: Gräßler J, von Borstel U
Journal: Pferdeheilkunde Equine Medicine
Summary
# Editorial Summary: Fructan content in pasture grasses Gräßler & von Borstel (2005) investigated whether a commercially available colorimetric method could reliably measure fructan content in pasture grasses, given that excessive fructan intake is implicated in laminitis development and that the gold-standard HPLC technique is too costly for routine farm-level screening. Four common grass species were sampled across the grazing season (April–November) and at conservation time (July), then analysed using both HPLC and the colorimetric method to compare their outputs. HPLC detected fructan concentrations ranging from 83–299 g kg⁻¹ dry matter (mean 154 g kg⁻¹), whereas the colorimetric method yielded substantially lower readings of 5–238 g kg⁻¹ (mean 82 g kg⁻¹), with discrepancies varying by species and sampling date; further investigation showed the colorimetric technique's fructan-digesting enzymes failed to hydrolyse fructans completely, systematically underestimating true fructan load. For practitioners managing laminitis-prone horses, these findings underscore that the colorimetric method cannot reliably guide dietary decisions, and that despite cost barriers, accurate fructan assessment of pasture and conserved forage requires laboratory HPLC analysis rather than reliance on cheaper alternative techniques.
Read the full abstract on PubMed
Practical Takeaways
- •If you need to measure pasture fructan content to manage laminitis-susceptible horses, use HPLC rather than cheaper colorimetric methods—the cost difference is justified by accuracy.
- •Understand that your pasture's fructan content varies significantly by season (April-November sampling) and grass species, so single measurements may not represent current risk.
- •Be aware that simple field-based or budget testing methods for fructans are likely to underestimate the actual content, potentially leaving susceptible horses at greater risk than you realize.
Key Findings
- •HPLC analysis of pasture grasses showed fructan content ranging from 83-299 g/kg dry matter (mean 154 g/kg), with substantial seasonal and species variation.
- •Colorimetric method significantly underestimated fructan content (mean 82 g/kg) compared to HPLC, with discrepancies varying by sampling time and grass species.
- •Incomplete fructan hydrolysis by enzymes used in the colorimetric method resulted in unreliable measurements for equine pasture assessment.
- •The commercially available colorimetric method is not suitable for accurate fructan quantification in horse pastures and HPLC remains the reference standard.