Table 2 Main parameters used in the bio-economic herd model. The indices i and b refer to the age-sex cattle class (calf, heifer, young male, cow, adult bull and adult ox) and breed respectively
Category | Notation | Parameter |
|---|---|---|
Production | m b | Milk yield for breed b (kg per lactation) |
l b | Lactation length in breed b (days) | |
c b | Annual calving rate in breed b | |
w i,b | Live-weight of animals in class i and breed b, (kg) | |
Herd management | o i | Annual offtake rate of animals in class i |
D | Draught yield of oxen (days per year) | |
V | Proportion of AAT deaths salvaged | |
Impact of AAT on productivity | r l | % reduction of milk production in animals affected by AAT |
r f | % reduction in fertility in animals affected by AAT | |
r w | % reduction in live-weight in animals affected by AAT | |
r d | % reduction in draught power in animals affected by AAT | |
Incidence and mortality | T | Proportion of AAT cases successfully treated |
δ s | Duration of symptoms when treatment succeeds, in days | |
δ f | Duration of symptoms when treatment fails (days) | |
f i | Fatality rate of AAT when treatment fails in animals of class i | |
μ i | Baseline mortality in animals of class i, i.e. when AAT incidence = 0 |