Mathematical modeling of the relationship of feed efficiency, days to market weight, and costs of production.

Decreased feed efficiency and increased days to market often occur together causing an increase in production costs. By mathematical modeling, the effect of decreased feed efficiency on the growth of an animal is given and the resulting formulas for increased days to market are derived. The most general model discussed incorporates the effects on days to market weight of variable feed efficiency (above or below normal for that species) and weight loss with a subsequent growth set-back. The resulting predicted increased days to market compares well with experimental data and examples using published data are discussed. This modeling allows a good estimate of the increased costs of production due to finishing unthrifty animals, which takes into account all the variable daily costs, not just the increased total feed consumption during the period of growth to market weight.