ARS | Publication request: MODELLING GRASS UTILIZATION BY DAIRY COWS

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: October 30, 1998
Publication Date: N/A

Technical Abstract: The efficient utilization of grass after it is produced is key to sustainability for many dairy farming systems. Models which can predict performance are important to improving efficiency. Accurate prediction of intake, which accounts for 60 to 90% of the variation in animal performance, is critical to this modeling effort. Of the many factors influencing intake, the animal factors of milk production and liveweight change, and the plant factor of neutral detergent fiber appear to most affect predictions of intake, regardless of situation. Digestion kinetics and passage are the primary processes involved in digestion. In modeling digestion, it is important to understand and be able to accurately measure the factors influencing the indigestible fraction, rate of digestion, and lag. For passage we must be able to model rate of escape and particle size reduction. There are many factors involved in modeling intake, digestion, and ultimately animal performance. Some modelers prefer complex models wit a low level of aggregation while others have suggested that it might be more prudent to use models which are limited to more specific situations. Whatever approach is used, it is important to understand the biology involved before modeling can take place. A systems approach involving modeling and focusing on the myriad of interactions involved in the intake, digestion and metabolism of grass forages should lead to improved grass utilization efficiency.