These assumptions are listed below. Breeding and weaning occur at distinct times during the year. All enterprises last at least one month.
Weight gain occurs linearly.
The energy requirements for offspring are included in the needs of their lactating dams until 3.5 months for calves and 12 weeks for lambs and kids. Purchased animals have the same reproductive calendar, mortality rates, culling rates, daily energy requirements and reproductive statistics as similar animals already in the herd. Supplemental feeding for stockers and feeders is distributed in proportion to time spent in the enterprise during each year. Changes in animal populations occur at discrete times and in a prescribed order of occurrence. Stockers and feeders are sold within 24 months of the inventory date of the year they are obtained, and those present on the inventory date are sold within twelve months.