Model Assumptions

We used a number of assumptions within our future projections model. Those assumptions are listed below:

• Breeding herds give birth once annually; cows first calve at two or three years of age, and ewes or does first give birth at one or two years of age.
• Breeding and weaning occur at distinct times during the year.
• All enterprises last at least one month.
• Weight gain occurs linearly.
• Average gestation lengths are 285 days for cattle, 147 days for sheep, and 152 days for goats.
• Average birth weights are 36 kg for calves, 5 kg for lambs, and 5 kg for kids.
• Half of the offspring produced are expected to be male and half are expected to be female.
• 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 present 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 12 months.
• Feeder lambs and kids are shorn no more than once between being obtained and being sold, and shearing occurs, if at all, in the year they are sold.
• For animals leaving an enterprise, direct costs are incurred in proportion to time spent within the enterprise.