Information was gathered from dairy farms in four regions of New Zealand for the season ending May 2010. The regions were Waikato, Taranaki, Canterbury and Southland. Two farms were selected from each region, one that had undertaken regrassing on a regular basis for at least five years (Modern Varieties, MV) and the other had not undertaken any regrassing in the previous decade (Traditional Varieties, TV). A computer simulation tool (UDDER) was used to model the effect of regrassing on these farms. In three regions, MV generated more milksolids/ha and a greater net farm margin compared with TV. The use of computer modelling allows farmers to make a decision based on the data from their own property rather than rely on data that is sourced from different growing conditions. Keywords: regrassing, modern varieties, traditional varieties
