EFFICIENCY OF BEEF-PRODUCTION SYSTEMS - DESCRIPTION AND PRELIMINARY EVALUATION OF A MODEL

A deterministic beef efficiency model (BEM) was developed for investig ating production efficiency. Efficiency was defined over the lifetime of the herd, as a ratio of total output (lean meat equivalent) from th e herd to total input (feed equivalent in Meal metabolizable energy, M E) to the herd, and has units of g lean meat M cal(-1) ME. The model c ombines three tandem submodels describing: (1) growth and feed intake, (2) herd structure, and (3) enterprise efficiency. It is capable of i nvestigating efficiency of production in traditional cow-calf systems, dairy-beef systems as well as systems where an offspring's sex-ratio at birth is controlled. It treats the female and her offspring as the basic herd unit and evaluates efficiency in relation to how long the c ow stays in the herd (age at culling) and the degree of maturity of he r offspring when marketed. Procedures for validating and evaluating be haviour of a beef efficiency model are described. The model was most s ensitive to the degree of maturity of the dam. Increasing the dam's ma turity by 10% resulted in a large (up to 35%, depending on breed group ) decline in efficiency. The model was moderately sensitive to maturin g rate and carcass lean content but was not sensitive to mature size o r the inflection parameter. Increasing the maturing rate or lean conte nt by 10% results in up to 8.7% increase in efficiency. (C) 1997 Elsev ier Science Ltd.