Project Number: 1907-31000-006-00
Project Type: Appropriated

Start Date: Aug 02, 2007
End Date: Aug 01, 2012

Objective:
1. Incorporate changes to improve the prediction of wasteful ammonia production in the rumen and assess alternative strategies of reducing nitrogen losses. 2. More accurately describe the impact on energy spilling and pH on microbial growth efficiency and other factors in the model to improve its application to feeding dairy cattle.

Approach:
The rumen will be programmed and simulated using an object-oriented language (Stella). This approach will: 1) estimate ruminal feed degradation and passage from standard methods of feed description, 2) correct microbial growth efficiency for maintenance energy experiments, 3) accommodate hyper-ammonia producing bacteria (HAB), 4) trigger energy spilling when microbial growth is limited by factors other than energy (e.g. ammonia, amino acids or low pH), and 5) estimate ruminal pH from the amount of VFA generated, VFA dilution from the rumen, ruminal buffering and ruminal mixing motions. Sensitivity analyses will be conducted to identify critical parameters. Coefficients will be adjusted until the outputs from the model closely match results found in the research literature. Milk production will be estimated by linking outputs from rumen model to the animal equations of the Dairy NRC (2001).