Feed the ewe for the lamb
Ewe nutrition in the last six weeks sets birth weight, colostrum supply and mothering. Very small and very large lambs are both at higher risk.
Flock Management
Lamb Mortality Rate Calculator
Enter the lambs born and the lambs lost at each stage. The calculator gives your overall lamb mortality rate, the survival rate and a breakdown showing where the losses happened, which is what tells you where to look.
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Your result
Lamb Mortality Rate Calculator result
Lamb mortality rate12%
Around the average for many flocks, with room to improve.
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Estimates for planning only. Results depend on the figures you enter and on typical published values, and real animals and farms vary. Consult a qualified veterinarian, nutritionist or adviser before making animal health, feeding or financial decisions.
The breakdown
Updates as you type- Lambs lost
- 18
- Lambs surviving
- 132
- Survival rate
- 88%
The basics
What Is Lamb Mortality Rate?
Lamb mortality rate is the percentage of lambs born that die before weaning, counting stillborn lambs. A flock that loses 18 of 150 lambs born has a 12% lamb mortality rate and an 88% lamb survival rate.
The Lamb Mortality Rate Calculator divides lambs lost by lambs born and multiplies by 100, then splits the losses into 3 stages: born dead, first week and week one to weaning. The 4 main causes of early lamb loss are starvation, hypothermia (cold exposure), dystocia (difficult birth) and infection.
What the Lamb Mortality Rate Calculator Calculates
The Lamb Mortality Rate Calculator returns 4 results:
- Mortality rate: lambs lost as a percentage of lambs born
- Survival rate: lambs alive at weaning as a percentage of lambs born
- Lambs lost and surviving: head counts for the flock
- Stage breakdown: losses at birth, in week one and before weaning
When to Use the Lamb Mortality Rate Calculator
There are 3 main uses for the Lamb Mortality Rate Calculator:
- Review lambing results at weaning
- Locate the stage with the highest lamb losses
- Measure the effect of changes to housing, colostrum or vaccination
Getting started
How to Use the Lamb Mortality Rate Calculator
To use the Lamb Mortality Rate Calculator, follow 3 steps: count every lamb born, then split the losses by stage, then read the breakdown. The result updates as you type.
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Step 1: Count every lamb born
Include stillborn lambs. Leaving them out hides the losses that happen around birth.
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Step 2: Split the losses by stage
Born dead, lost in the first week and lost before weaning each point to different causes.
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Step 3: Read the breakdown
The longest bar is where to put your effort before next lambing.
The maths
Lamb Mortality Rate Formula
Mortality rate is lambs lost as a share of all lambs born.
Mortality rate (%) = Lambs lost ÷ Lambs born × 100
Survival rate is 100 minus the mortality rate. Count lambs born dead in both the births and the losses.
Worked example
- Lambs born 150
- Lambs lost 6 + 8 + 4 = 18
- Mortality rate 18 ÷ 150 × 100 = 12%
- Survival 132 lambs, 88%
Reference
What Lamb Losses at Each Stage Point To
The timing of a death narrows down the likely cause.
| Stage | Common causes |
|---|---|
| Born dead | Abortion, difficult or prolonged lambing, underfed ewes in late pregnancy |
| First week | Starvation and cold exposure, too little colostrum, mismothering, navel and joint infections |
| Week one to weaning | Clostridial disease, pneumonia, coccidiosis, worms, predators and accidents |
Most lamb deaths happen in the first few days of life, so that is usually where the largest gains are.
Glossary
Lamb Mortality Rate Terms Explained
6 terms appear in the Lamb Mortality Rate Calculator and in the guidance around it.
Stillborn lamb
- A stillborn lamb is born dead at full term. Stillborn lambs count in lambs born and in lambs lost.
Hypothermia
- Hypothermia is a body temperature below 39°C (102°F) in a young lamb. Wet, small and unfed lambs chill first.
Dystocia
- Dystocia is a difficult or prolonged birth, caused by an oversized lamb or a lamb in the wrong position.
Watery mouth
- Watery mouth is an Escherichia coli (E. coli) infection of lambs in the first 3 days of life, linked to low colostrum intake and dirty pens.
Joint ill and navel ill
- Joint ill and navel ill are bacterial infections that enter through the wet navel. Iodine on the navel at birth lowers the risk.
Post-mortem
- A post-mortem examination by a vet identifies the cause of death and directs the changes for the next lambing.
Good to know
How to Reduce Lamb Losses
3 habits reduce lamb losses: feeding the ewe in late pregnancy, fast colostrum and a record of every death.
Colostrum, quickly
A lamb needs colostrum within the first hours of life for energy and antibodies. Lambs that miss it are the ones that fade over the following days.
Record every death
A simple tally of date, age and likely cause shows patterns you cannot see from memory. Ask your vet to examine lambs when losses cluster.
Answers
Frequently Asked Questions
Common questions about the lamb mortality rate calculator and the numbers behind it.
What is a normal lamb mortality rate?
Many flocks lose between 10 and 20% of lambs born. Well-managed flocks keep total losses to 10% or less.
When do most lamb deaths happen?
In the first few days. Losses around birth and in the first week usually account for most deaths, with starvation, cold exposure and difficult births the leading causes.
Should stillborn lambs be counted?
Yes. Lambs born dead are part of the flock’s reproductive loss and often share causes with early deaths. Counting them gives the true picture.
How do I work out lamb survival rate?
Subtract the mortality rate from 100. If 12% of lambs born were lost, the survival rate to weaning is 88%.
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