Seasonal and Diurnal Variation in Water-Soluble Carbohydrate Concentrations of Repeatedly Defoliated Red and White Clovers in Central Kentucky.
Authors: Kagan Isabelle A, Anderson Meredith L, Kramer Kelly J, Seman Dwight H, Lawrence Laurie M, Smith S Ray
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Pasture-grazing horses face variable exposure to water-soluble carbohydrates (WSCs) depending on when and what they graze, yet little is known about how clover—a common legume in mixed pastures—accumulates these rapidly fermentable compounds across seasons and times of day. Kentucky researchers monitored red and white clover cultivars throughout the grazing season (April–October 2015), harvesting samples in both morning and afternoon after four weeks of regrowth to quantify WSCs and starch content. White clover accumulated approximately 14% more WSCs than red clover by September, and critically, both species showed dramatic diurnal variation, with afternoon starch concentrations exceeding morning levels by nearly threefold (31–40 mg/g morning versus 150 mg/g afternoon on average). For practitioners managing horses prone to laminitis, equine metabolic syndrome, or colic, these findings suggest that afternoon grazing on clover-dominant pastures presents substantially higher nonstructural carbohydrate intake than morning turnout—a distinction that warrants consideration in pasture management and supplementary feeding strategies, particularly in late summer when WSC accumulation peaks. Although the authors acknowledge that further work is needed to establish whether mixed grass-legume pastures in this region reach concentrations sufficient to trigger clinical disease, the magnitude of variation documented here justifies implementing grazing restrictions during peak afternoon hours for at-risk individuals.
Read the full abstract on PubMed
Practical Takeaways
- •Grazing times matter: afternoon grazing exposes horses to significantly higher carbohydrate loads (particularly starch) compared to morning grazing, relevant for metabolically compromised horses
- •White clover monocultures present higher WSC risk in late summer/fall; consider pasture composition and grazing management for horses prone to laminitis or metabolic disease
- •Current data from pure clover plots may not reflect mixed grass-legume pastures typical in Kentucky; wait for further research before making major management changes based on these findings alone
Key Findings
- •Water-soluble carbohydrate concentrations in red and white clovers ranged from 80-99 mg/g (freeze-dried basis) across the grazing season April-October
- •White clover contained 14% more WSCs than red clover in September (P < 0.0001)
- •Afternoon WSC concentrations were 10% higher than morning (P < 0.0001), with starch concentrations 290% higher in afternoon
- •Combined nonstructural carbohydrate concentrations reached 150 mg/g in afternoon samples, but risk to mixed grass-legume pastures remains undetermined