BIOECONOMIC EVALUATION OF EMBRYO TRANSFER IN BEEF-PRODUCTION SYSTEMS .1. DESCRIPTION OF A BIOLOGICAL MODEL FOR STEER PRODUCTION

Concepts used to derive a deterministic model for evaluating embryo transfer for commercial steer production taking into consideration genetic merit for growth and mature size, herd feed supply, and recipient maternal environment are discussed. Genetic potential of an embryo is used to derive optimal growth rates that can be sustained by available herd feed per animal per day. Equations are provided for various measures of performance as functions of the feed, genotype of the embryo, and recipient maternal contribution. To assess the value of a particular line of embryos, interactions between genotype and nutrient environment are quantified, so that the benefits of embryos of high genetic merit are evaluated objectively. Product quality and weight are predicted from the model to provide a framework that will allow commercial beef producers to determine marketing strategies likely to result in optimal return.