A marginal income and cost analysis of the effect of nutrient density on the performance of white leghorn hens in battery cages1

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Abstract
In an experiment lasting 40 weeks with 576 caged White Leghorn (WL) hens and using linearly programmed least‐cost rations, the influence of increasing the nutrient density by increments of 100 kcal metabolisable energy (ME)/kg food, within the range 2500 to 3200 kcal ME/kg, on production was studied. Increasing the nutrient density was accompanied by increases in egg weight, body weight and ME intake/hen d but mortality and the number of eggs laid were not affected (Pegg and body weight in determining the most profitable nutrient density were at least as important from the economic point of view as the influence of the increased ME intake caused by increasing nutrient density. In the price situations considered, they neutralised the effect of one another, so that the diets with the lowest cost per calorie were also the most profitable. For every price situation of raw materials, eggs and hens, the economical optimal food composition can be quickly and accurately determined by making use of the marginal profit analysis. It is also possible to couple the regression analysis for the adaptation of the mathematical functions to the parametric computer program which calculates the least‐cost rations.