Management

The mortality over the mortality days expressed as a percentage.

To determine a more realistic profit margin over food cost the wastage is added to the food consumed by the bird and does not influence the displayed biological efficiencies. Wastage should be entered as a percentage of total food consumption. The purpose of this option is to allow for an opportunity to account for old or badly designed feeders, causing feed wastage and giving an idea of the cost of this wastage and the ultimate impact on the profitability of the operation.

These are given in the form of histograms that show the rate at which birds die at different periods during the simulation.

Notes:

1. If a mortality pattern is used in several experiments, and it is edited here, then it is changed in all the experiments.
2. The default mortality pattern is based on equations published by Grosskopf & Matthäus, (1990) Syst. Anal. Model. Simul. 7: 473-491.

The mortality calculated for the currently selected day is displayed above the histogram, as a percent per day. The mortality for each day is calculated using the following rules:

1. The mortality during each period is proportional to the size of the bar. For example, a day with a bar twice the size of that of another day will have twice the mortality.
2. The mortality during each day is calculated so that the total mortality over the mortality days, is equal to the total mortality specified.
3. If all the bars over the mortality days are set to zero, the mortality will be zero throughout the entire simulation, irrespective of values entered elsewhere.
4. The mortality over a particular period cannot exceed 100%, and in the unlikely case that the mortality over a period is calculated as 100%, the simulation will end when that period is reached.

The importance of an accurately described pattern of mortality cannot be stressed enough. This can be defined by adjusting the histogram or specifying the daily mortality percentage. Below are three examples of a default, early and late mortality, all having varied economic impact on feed conversion and profitability.

A histogram is used to describe the extent to which husbandry influences the potential growth of the broilers. If husbandry conditions are perfect (non-limiting) all the bars should be placed at the maximum (1.0) (the default condition). Examples of constraints to performance that could be simulated in this way would be that of a vaccine reaction or a disease challenge. If it is known, for example, that a vaccine reaction has the effect of reducing the growth rate by 0.05 to 0.15 of the potential over the period 7 to 13 days of age, the bars corresponding to that time period should be lowered accordingly. In this way, a more accurate simulation of growth may be obtained. Excessive temperatures and stocking density are inherently dealt with by the program to determine the constraining effects on feed intake and hence growth; there is no need to account for these by manipulating the husbandry constraint. For further details on stocking density see Stocking schedule or Actual growth data to determine whether stocking density is indeed a limiting factor. For further information on stressors refer to the publication by Wellock, I.J., Emmans, G.C. and Kyriazakis, I. (2004) Modelling the effects of stressors on the performance of populations of pigs. Journal of Animal Science 82, 2442-2450.