Insulin Resistance – Comparison of Methods of Fructan Analysis in UK Pasture Grasses

Article Outline

• Take Home Message
• Introduction
• Materials and Methods
• Results
• Discussion
• Clinical Relevance
• Conclusion
• Copyright

Back to Article Outline

Take Home Message 

Values for fructan in grass determined by a colorimetric method (McCleary) were consistently lower than those obtained by HPLC. This discrepancy was at least partially due to incomplete hydrolysis of grass fructan by the McCleary fructanase.

Back to Article Outline

Introduction 

Insulin resistance (IR) is associated with elevated intakes of WSC. WSC comprise simple sugars and fructans (oligo-or polyfructosyl sucrose). To enable appropriate ration formulation for IR horses, it is important that WSC components can be quantified accurately. Two methods are mainly used to analyse fructans, an enzymatic/colorimetric method and an HPLC technique. The former relies on quantification of monomers released after fructan hydrolysis by fructanase. Some values for grass fructan using this method seem low. Therefore, the fructan values obtained by both techniques were compared.

Back to Article Outline

Materials and Methods 

Samples of Phleum pratense, Dactylis glomerata and Lolium perenne were analysed for fructan by both the colorimetric and HPLC methods. Selected samples were then analysed by HPLC both before and after fructanase treatment.

Back to Article Outline

Results 

Values obtained by the McCleary method ranged from 10 to 94 percent of those obtained by HPLC. Post-fructanase treatment analysis revealed incomplete (28-50%) hydrolysis of grass fructan.

Back to Article Outline

Discussion 

Fructans in these grass samples were differentially sensitive to the fructanase employed in the McCleary method.

Back to Article Outline

Clinical Relevance 

If using fructan values for grass forage obtained by the colorimetric method for IR equid ration formulation, the efficacy of the fructanase against the forage should first be determined

Back to Article Outline

Conclusion 

The colorimetric method may yield artificially low values for grass fructan.