FACTORS AFFECTING VOLUME AND SPECIFIC-GRAVITY MEASUREMENTS OF NEUTRALDETERGENT FIBER AND FORAGE PARTICLES

Pycnometers were used in this series of experiments to measure the spe cific gravity of the solid fraction in forage particles and to assess the effect of solubilization of DM on functional specific gravity and the specific gravity of the solid fraction. The removal of cell conten ts by either neutral detergent extraction or DM solubilization decreas ed functional specific gravity and the specific gravity of the solid f raction of particles, Solutes increased the specific gravity of gas-fr ee distilled water in proportion to the amount of soluble DM dissolved . The average specific gravity of the solids in particles extracted by neutral detergent and the insoluble DM in alfalfa particles averaged 1.48 and 1.50, respectively. The effect of forage species and method o f forage preservation on specific gravity of the solids in forage part icles was minimal. However, during partial solubilization of DM, the l oss of mass averaged 1.9 times the loss of volume, indicating that min erals were the primary solute responsible for the change in specific g ravity of particles. The biological meaning of functional specific gra vity is unclear because it excludes the liquid associated with particl es. However, functional specific gravity of stem particles passing a 4 25-mum sieve was identical to specific gravity of the solids, indicati ng the absence of gas in these particles.