A method is disclosed for calculating a transition monitor value for one or more milk-producing animals so as to enable its use in evaluating and optimally managing the health and productivity (i.e., the transition performance) of those individual animals and of their herds. An expected milk production is calculated for a given time period of a current lactation based both on the individual's performance in her previous lactation and on her current state. Transition monitor values are calculated as the difference between actual and expected milk production values. The transition monitor values can then be used to evaluate and to optimize the health and productivity of both individuals and herds of individuals and to make comparisons of transition monitor programs both within and between herds.