Effects of storage-handling methods on nutrient analysis of fresh-forage samples.
Authors: Kerley B S, Harris P, Lea K, McClendon M, Adams A A
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Storage Methods and Forage Analysis Accuracy For horses with insulin dysregulation, precise forage analysis—particularly nonstructural carbohydrate (NSC) values—is critical for dietary management, yet the pre-analytical handling of samples can significantly skew results. Kerley and colleagues investigated how five different storage protocols (microwave-oven freezing, room temperature, 3°C, −20°C, and −80°C) affected nutrient composition of fresh pasture samples from mixed grassland and ryegrass plots stored for either 24 hours or one week before laboratory analysis via wet chemistry and near-infrared spectroscopy. Room-temperature storage proved particularly problematic for mixed grass, causing water-soluble carbohydrates, ethanol-soluble carbohydrates, and NSC to decrease significantly between 24 hours and one week; conversely, ultra-low freezing (−80°C) reduced crude protein in ryegrass and starch values after extended storage, whilst −20°C storage and microwave treatment sometimes paradoxically increased certain nutrient values over time. The practical recommendation emerging from these findings is straightforward: samples collected from pasture should be placed on ice immediately and refrigerated at 3°C (standard fridge temperature), where they remain stable for up to one week before shipment for analysis, avoiding both metabolic degradation at room temperature and the artifactual changes introduced by extreme freezing protocols. This standardised approach will help ensure that NSC readings accurately reflect the true forage composition available to your horses.
Read the full abstract on PubMed
Practical Takeaways
- •Do not store forage samples at room temperature as carbohydrate values can decrease significantly within 24 hours to 1 week, compromising accuracy of NSC analysis critical for ID horses
- •Transport fresh forage samples on ice immediately after collection to a refrigerated location (3°C) and keep refrigerated until shipment for analysis to maintain nutrient integrity
- •Avoid ultra-cold freezing (-80°C) for forage samples as this storage method can paradoxically alter starch and protein values, making results unreliable for dietary management decisions
Key Findings
- •Mixed grass stored at room temperature showed significant reductions in WSC (P=0.009), ESC (P=0.001), and NSC (P=0.006) from 24h to 1 week
- •Ryegrass ESC and starch decreased at -80°C storage (P=0.007; P=0.001), while mixed grass CP decreased under the same conditions (P=0.02)
- •CP of ryegrass increased and ESC of mixed grass increased when stored at -20°C and microwave-oven treated respectively over time (P=0.02; P=0.03)
- •Refrigerated storage (3°C) with ice transport preserves nutrient composition more reliably than room temperature or ultra-cold storage (-80°C) for up to one week prior to analysis