Better Diagnostics = Greater Herd Value
Positive MAPfast Result Decision Option Value
Option 1 — Early culling
Cash flows (per cow)
- Cost: Replacement heifer: –$1,800
- Benefit: Salvage value: +$600
- Avoided milk loss: +$1,800
- Avoided clinical disease cost: +$800
- Avoided transmission cost: +$1,000
Net economic impact: +$2,400
Expected net gain ≈ +$2,400 per early‑culled MAP‑positive cow
Probabilities
- Remains low‑shedding, productive: p = 0.5
- Progresses to high‑shedding / clinical: p = 0.5
Direct costs
- Extra testing + labor + infrastructure: –$300 (NPV over remaining life)
Scenario A — stays subclinical (p = 0.5)
- Milk loss smaller: –15% → –$900
Transmission risk 0.2
- Expected transmission cost:
- (0.2 \times $2500 = $500). -$500
- Clinical disease cost largely avoided:
- (vs full $800) +$600
Net for Scenario A branch: -$1,100
Scenario B — progresses (p = 0.5)
- Essentially similar to “no intervention"–$3,800
Expected value: 0.5x-$1,100 + 0.5x -$3,800
Expected net loss ≈ –$2,450 per MAP‑positive cow
Costs (per cow)
- Milk loss: –$1,800
- Clinical disease + extra culling: –$800
- Transmission cost: –$1,000
- Lower salvage value / emergency cull: –$200
Expected net loss ≈ –$3,800 per MAP‑positive cow
Example Assumptions:
Assumptions (per MAP‑positive cow, over remaining productive life)
- Baseline remaining lifetime milk margin: $6,000
- MAP‑related milk loss if kept: –30% → –$1,800
- Future clinical disease + treatment + extra culling cost: –$800
Transmission cost (new infections caused by this animal):
- Probability of infecting ≥1 replacement: 0.4
- Expected cost per infected replacement (lifetime loss): $2,500
- Expected transmission cost: (0.4 \times $2,500 = $1,000)
- Replacement heifer cost: $1,800
- Salvage value of culled cow: $600