Defining a breed
The Growth parameters tab of the breed details show the values that the model requires to simulate the potential growth of a male bird with the given genotype. Conceptually this is considered to be typical of the breed. Female growth parameters are automatically calculated by the program, using the data entered for male birds.
The data required are the empty body weight of the bird at maturity; the fat content of the bird at maturity (as a percentage of body weight); and two values that represent the rates of maturing of body protein and feather protein. A new user should initially use the default values provided with the model. With experience and during the support period these values can be refined to reflect more accurately the breed being simulated.
Note that the values should not be guessed; they can be determined or assessed systematically. Also it is important to note that the breed values should not be adjusted to achieve a given end point for the simulation. The Growth parameters determine the potential performance of the breed, not the performance observed under a given set of environmental conditions.
Options for Rate of feathering are Very Slow, Slow, Normal, Fast, Very Fast or User. These values are interpreted relative to the Rate of Maturing coefficient (B). The values are multiples of B; being 1.10 for very slow, 1.23 for slow, 1.36 for normal, 1.43 for fast and 1.50 for very fast feathering birds. The user-defined option allows the user to enter a specific value for the Rate of Feather Maturing. This may be changed under the Options/Broiler settings menu.
Potential growth graph
The effect of the growth constraint on potential growth is shown on the graph displayed under the growth parameters table. The graph is updated as soon as one of the relevant variables, or the growth constraint is changed. The various lines on the graph may be shown or hidden by selecting them in the checkboxes on the right.