COMPARISON OF SAMPLE PREPARATION METHODS FOR THE DETERMINATION OF THE RUMEN DEGRADATION CHARACTERISTICS OF FRESH AND ENSILED FORAGES BY THE NYLON BAG TECHNIQUE

摘要

A study was conducted to determine the best method of preparation of silage and freshly cut forage samples for the estimation of rumen degradability by the nylon bag technique. Three types of forage were evaluated: a grass silage, a fresh grass (ryegrass) and a fresh legume (white clover). For each forage, six preparation methods were compared: chopping fresh (FRS); chopping and macerating fresh (FMC); chopping, freezing, thawing and macerating (FRZ); freeze-drying (FD); low-temperature oven-drying (45 degrees C, 72 h) (OVD); high-temperature oven-drying (160 degrees C, 90 min) (DHD). Dried samples were hammer-milled (2.5-mm screen). Chemical composition and rumen degradability were affected by the method of preparation. Protein fractions were sensitive to drying method, and oven-drying reduced nitrogen (N) solubility and degradability as the severity of the heating was increased. OVD and DHD gave lower estimates of N and dry matter (DM) solubility and degradability than FD. The effect of drying method an DM degradability was to reduce solubility and effective degradability, calculated for an outflow rate of 0.033 per h, but not potential degradability.