GENERAL CATTLE PRODUCTION SYSTEMS-MODEL .2. PROCEDURES USED FOR SIMULATING ANIMAL PERFORMANCE

The methods used for simulating animal performance in the Texas A&M Cattle Production Systems Model are given and discussed. The GRO subroutine is used to calculate feed intake, changes in weight and skeletal size and, if appropriate, milk production level. Growth rates from the GRO subroutine, size, condition, time since calving and the fraction of the animals in the class that were in oestrus the previous month are used in the FERT subroutine to simulate the occurrence of oestrus and conception in open, breeding females. Death rates are simulated in the DIE subroutine as functions of the time of the year, the age and condition of animals in the class and, for cows, whether or not they calved during the current or previous month. The information from these subroutines is used to update the numbers and characteristics of animals in the various classes at the end of each month of simulation. © 1979.