Abstract

Forage particle size has long been recognized as the key intricate factor determining ration contents of physically effective neutral detergent fibre, which in recent years has become the most important consideration in advanced dairy feed formulation for the rumen health, milk yield and welfare of the dairy cows. Fine chopping reduces particle size, resulting in reduced forage dry matter intake, lower retention period of digesta, decreased digestibility of fiber, inconsistent quality of ruminal mat, decreased milk yield, depression of milk fat, and health issues secondary to sub-acute ruminal acidosis. Similarly, excessive coarse forage particles may be lead to reduced total nutrient intake, poor digestibility of organic matter, reduced milk yield and quality, and compromised overall performance. The rumen is a constant fermentation vessel, containing vast amounts of hydrogen ions that can only be stabilized by a proper salivary buffer balance obtained through intake of sufficient effective neutral detergent fibre and its optimal duration. The overall impacts of particle size, however, depend on forage type, forage to concentrate ratio and, fermentability characteristics of the organic matter in the formulated ration. In general, 8-19 mm particle size irrespective of forage type measured on Penn State Particle Separator may be considered optimum for practical dairy feed formulation. © 2021. All Rights Reserved.