Relationships among Body Condition, Insulin Resistance and Subcutaneous Adipose Tissue Gene Expression during the Grazing Season in Mares.
Authors: Selim Shaimaa, Elo Kari, Jaakkola Seija, Karikoski Ninja, Boston Ray, Reilas Tiina, Särkijärvi Susanna, Saastamoinen Markku, Kokkonen Tuomo
Journal: PloS one
Summary
# Editorial Summary Pasture quality significantly influences metabolic changes in grazing mares, with horses on cultivated high-yielding grass developing higher body condition scores (7 vs 5.4), greater body weight (618 kg vs 572 kg) and increased waist circumference compared to those on semi-natural grassland over a four-month grazing season. Sixteen Finnhorse mares were monitored from May through September with measurements of body condition, intravenous glucose tolerance testing (IVGTT) and subcutaneous adipose tissue gene expression at both timepoints, revealing that richer pasture resulted in greater basal and peak insulin concentrations and faster glucose clearance rates, though frank insulin resistance did not develop. Gene expression profiling demonstrated consistent seasonal patterns across both groups—notably downregulation of insulin receptor, leptin, retinol binding protein 4 and monocyte chemoattractant protein-1, alongside upregulation of adiponectin and stearoyl-CoA desaturase—suggesting adaptive metabolic responses to the grazing season independent of pasture type. These findings have important implications for laminitis risk management, indicating that whilst cultivated pastures promote metabolic stress markers and increased insulin secretion in mares, strategic grassland management may offer protective effects without necessarily triggering the pathological insulin resistance that precedes developmental orthopedic disease; practitioners should consider pasture composition as a modifiable risk factor in metabolically predisposed individuals.
Read the full abstract on PubMed
Practical Takeaways
- •High-quality cultivated pastures increase body condition and insulin responses in grazing mares; monitor body condition and consider restricting grazing time or supplementing with lower-quality forage if laminitis risk is a concern.
- •Gene expression changes during grazing season suggest adaptive metabolic responses; these protective mechanisms may break down under extreme obesity, so weight management remains critical for laminitis prevention.
- •Semi-natural grassland grazing maintains lower body condition scores and more moderate metabolic responses compared to cultivated pasture, making it a potentially safer option for metabolically at-risk mares.
Key Findings
- •Mares grazing cultivated pasture developed higher body condition scores (7 vs 5.4) and greater insulin responses during glucose tolerance testing compared to semi-natural grassland grazing.
- •Cultivated pasture grazing did not trigger clinical insulin resistance despite higher basal and peak insulin concentrations and faster glucose clearance rates.
- •Subcutaneous adipose tissue showed significant seasonal gene expression changes including downregulation of insulin receptor and leptin, and upregulation of adiponectin and stearoyl-CoA desaturase across both grazing conditions.
- •Positive correlations existed between adiponectin expression and its receptors, and between stearoyl-CoA desaturase and adiponectin in subcutaneous adipose tissue.