Juan Ku-Vera is the head of the Laboratory of Climate Change and Livestock Production at the University of Yucatan, Mexico. During the past thirty years, he has been involved in the nutritional evaluation of tropical feedstuffs for ruminants. Dr. Ku-Vera earned his PhD from the University of Aberdeen (Rowett Research Institute) in Scotland (mentor Prof. Bob Ørskov) investigating the energy and nitrogen metabolism of cattle. He carried out postdoctoral work on energy metabolism of dairy cows at the National Institute of Animal Science in Japan (mentor Dr. M. Shibata). At present, Dr. Ku-Vera is evaluating the effect of foliage of tropical trees and shrubs containing secondary metabolites (condensed tannins, saponins), on methanogenesis in cattle and sheep housed in respiration chambers. Recently, he has been investigating the net energy requirements for maintenance of tropical cattle by indirect calorimetry.