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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.

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