New Zealand dairy products account for 19% of the value of the country's exports. This high-value industry relies heavily on the ability of dairy cows to utilise forages as their main dietary staple. This is a big contrast to dairy operations in North America, where cows are fed grains and conserved forages of known chemical composition. In grazing systems, the quality of the pasture is an ever-changing playing field: weather, forage variety, level of fertilisation, and age of the plant are some of many factors influencing the quality of the cows' diet. The chemical composition of the forage, and hence its nutritive value, change from season to season, from paddock to paddock, from day to day and even within the same day!
Because experimentation in animal nutrition can be expensive and time consuming, a way to maximise chances of success in our research projects is through simulation of nutritional scenarios. GoldSim was used to simulate changes in the pasture chemical composition and their effects on the digestion by cows. In particular, the simulation aimed to replicate what happens in the forestomach of a lactating cow, and how the fermentation of the forage affects the amount of protein available to the cow for productive purposes.