Animal mortality rate calculator explained
The animal mortality rate calculator reconciles opening stock, births or placements, sales, and the closing head count to show how many animals died during the period. It also pulls disease case data into a case fatality percentage so you can separate overall losses from a specific outbreak. Use it when auditing broiler or swine houses, compiling NAHMS-style herd reports, or briefing veterinarians on recent case counts.
How the conversion works
Total deaths come from basic inventory math:
The mortality rate divides deaths by the available animals and expresses it as a percentage. Cumulative mortality uses the surviving herd (closing stock) in the denominator, while case fatality divides disease-caused deaths by confirmed cases:
\\text{mortality\\%} = \\frac{\\text{deaths}}{\\text{opening} + \\text{births}} \\times 100, \\quad \\text{case fatality\\%} = \\frac{\\text{disease deaths}}{\\text{disease cases}} \\times 100Units and conversions
| Quantity | Unit | Notes |
|---|---|---|
| Opening, births, sales, closing | head | Enter counts for one house, barn, or herd. |
| Deaths | head | Calculated from inventory reconciliation. |
| Mortality rate | percent | Relative to animals available during the period. |
| Cumulative mortality | percent | Relative to the closing herd, useful for lifetime reporting. |
| Case fatality | percent | Requires positive disease case counts. |
Worked examples
- Broiler flock audit
A site places 20,000 chicks, sells 300 culls, and ends with 19,200 birds. Disease tracking shows 80 deaths among 500 diagnosed cases.
Mortality rate . Case fatality .
- Dairy herd health review
Opening 450 cows, 30 calvings, 10 culls, and a closing count of 455. Five pneumonia deaths occurred among 40 treated cows.
Mortality rate ; cumulative mortality relative to the closing herd is . Case fatality equals .
Tips and pitfalls
- Verify sales, transfers, or condemned birds are recorded the same day to prevent double-counting mortality.
- Keep births or placements separate from purchases so replacement animals do not inflate the mortality denominator.
- Use the case fatality line only when diagnostic counts are reliable; otherwise leave disease cases blank to avoid misleading percentages.
- Compare current mortality against breed benchmarks to decide whether to escalate with veterinarians or nutritionists.