We are building a stochastic Monte Carlo model to represent real farm scenarios by simulating individual animal life events. This animal life cycle model simulates events according to reproduction protocols, genetic merit, production curves, and culling decisions for individual cow on a daily basis. Events follow herd-level stochastic distributions with animal-specific modifiers. There are 6 groups of animals in the model: Calves, Heifers I, Heifers II, Heifers III, Cows, and Culled animals. Calves are from birth to weaning with particular facility and nutrition care, and decisions of whether to keep calves on the farm are made during this stage. The Heifers I group are from weaning to breeding with stochastic growth rates. Heifers II group are from breeding initiation to close to calving, where estrus cycles, user-defined breeding programs, and continued growth are simulated. The Heifers III group are less than one month before parturition. In this period, they either enter the herd or are sold; replacements may also be purchased. Production events in the Cows group are determined by breed, parity, production-level lactation curves, stage of pregnancy, and health status. Also, events initiated by breeding protocols like insemination and drying-off. Culling may occur in any of the 5 stages and is determined by stochastic culling rates for a variety of reasons. The Culled group have maintenance and slaughter value calculated. The stages and events were programmed using well-established distributions from literature and expert opinion. Last day of a 3000-d simulation of a 1000-cow herd possibly resulted in a herd composed of 138 Calves; 808, 1203, 54 in Heifers I, II, and III, respectively, 1000 Cows and 3 Culled animals. The high number of young stocks illustrates the combined effect of using sexed semen and keeping all female calves. This animal life cycle model is a sub-model of the whole farm Ruminant Farm Systems (RuFaS) model, which will be able to simulate the effects of individual animal management on whole farm efficiency and productivity.