ABSTRACT
Isolated reports from Australia have indicated that it is possible to obtain high lactation yields with Friesian cows grazing tropical grass/legume pastures. In 1976, a system prototype for milk production in the humid tropics was developed in Turrialba, Costa Rica. An examination of the data leads to the conclusion that, under grazing conditions and low stocking rate, supplementing dairy cows may cause an increase in milk production. Perhaps the reason for the rather poor response to supplementation of grazing cows is the stage of lactation at which comparisons were made. As the cow enters her fifth or sixth month of lactation, further supplementation would be inefficient. Switch-back designs require the use of cows that are already in their downward phase of milk production. In Latin America, in general, there is a tendency to use high levels of supplements for cows of European blood and small amounts or none for the native or crossbred cows.
