Table 1 Adaptations made to the original cow model to obtain the goat model

Herd size

50

770

Birth-birth interval

55 weeks

52 weeks

Birth season

year-round

12 weeks

Gestation period

40 weeks

21 weeks

Non-gestation period

15 weeks

31 weeks

Dry period

8 weeks

-

Young animals

no heifers in the model

includes youngstock

Environment

2 environments

1 environment

Replacement rate (year^-1)

0.355

0.305

Culling rate (week^-1)

Lactation or age 1

0.0057

0.0029

Lactation or age 2

0.0052

0.0029

Lactation or age 3

0.0065

0.0029

Lactation or age 4

0.0067

0.0136

Lactation or age 5&6

0.0161

0.0136

Lactation or age 7&8

NA

0.0136

Probability distribution of the lactation numbers (for cows) or age (for goats) at the start of simulation

Lactation or age 1

0.337

0.285

Lactation or age 2

0.252

0.245

Lactation or age 3

0.173

0.211

Lactation or age 4

0.11

0.136

Lactation or age 5

0.088

0.067

Lactation or age 6

0.04

0.033

Lactation or age 7

NA

0.016

Lactation or age 8

NA

0.008

Infection from the environment

p = 1 – exp(−E(t))

p = 1 – exp(−Ê(t)/N)

Quantity of bacteria released by shedders in low, mid and high levels respectively, expressed in dimensionless units.

1, 1/30, or 1/3000

1*50, (1/30)*50, or (1/3000)*50

Probability of abortion

0.02

0.02*(40/21)