A linear programming model is defined in detail to describe an on-farm integrated beef production enterprise. The model includes cropping, feeding and breeding activities with their requirements for land, labor, animal housing and crop storage facilities. Net energy and digestible protein equations are used prior to the model construction to determine the nutrient requirements for cows, replacement heifers, feedlot heifers and steers, given weights and growth rates in young animals proportional to mature cow weights. A method for identifying the distribution of animals across different age groups is also described. Three enterprises with purebred cows of different mature size, each under typical Ontario farm conditions, are analyzed and interpreted.