Implementation of CTR Dairy Model Using the Visual Basic for Application Language of Microsoft Excel

The goal of the article is to implement the CTR Dairy model using the Visual Basic for Application (VBA) language of Microsoft Excel. CTR Dairy is a dynamic simulation model for grazing lactating dairy cows that predicts milk production and profit over feeding based on ruminal digestion and absorption of nutrients under discontinuous feeding schedules. The CTR Dairy model was originally developed as a research tool using a proprietary computer simulation software called SMART that required the SMART client to run the program. As SMART software is now discontinued, and its client is no longer available, rewriting the model in the VBA language using Microsoft Excel for inputs and outputs makes the program available to a broad range of users including dairy farmers, extension advisors, dairy nutrition consultants and researchers. Dairy farmers can use the new version of the CTR Dairy program to manipulate the herbage allowance and the access time to the grazing paddock, as well as the timing of supplemental feeding, to improve the utilization of the pasture and to increase the production of the milk.