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Replacement rate
In short
Replacing cows that leave the herd with heifers. The replacement rate is the share of the herd replaced each year.
What is herd replacement?
Herd replacement means topping up the dairy herd. Cows that leave the farm are replaced by heifers. These heifers come from your own rearing, from outsourced rearing or are bought in when in calf.
The replacement rate
The replacement rate is the share of the herd replaced by heifers in one year. The calculation is simple:
Replacement rate = number of heifers entering the herd per year / average number of cows x 100
An example: a farm with 100 cows brings 33 heifers into the herd in a year. The replacement rate is 33 per cent. The cows then stay in the herd for only about three lactations on average. Many farms in Germany are between 30 and 40 per cent.
Closely related is the culling rate: the share of cows that leave the herd each year. With a constant herd size, both are the same. If the herd grows, the replacement rate is higher.
Why does the rate matter so much?
In the German state of Schleswig-Holstein, rearing a heifer up to first calving cost €2,659 on average in 2024. A cow often only earns these costs back in her second lactation. If she stays for just three lactations, the profitable period is short. Every extra lactation lowers the rearing costs per litre of milk.
A worked example from practice: if the productive life on a farm with 100 cows rises from three to five lactations, 13 fewer heifer calves are needed. That alone saves about €21,000 in rearing costs per year. Because there is less youngstock on the farm, you can produce more milk within the same phosphate limit. You will find the full calculation in Aim for two more lactations.
Voluntary and involuntary culling
Not every cow leaving the herd is a bad sign. Voluntary culling, for example because of low yield or genetic progress, is part of management. Involuntary culling is the problem. In seven out of ten cases, a cow does not leave the herd by choice. The most common reasons are:
- Infertility
- Udder inflammation and a high cell count
- Claw and leg problems
- Metabolic disorders around calving
Around 18 per cent of cows already leave after their first lactation. This is where the biggest gains are: a better transition period, healthy claws and good udder health reduce the number of involuntary culls.
Age at first calving and youngstock needs
How many heifer calves you need to rear depends on the replacement rate and on the age at first calving. The later the heifers calve, the more youngstock is in the shed at the same time. An age at first calving of 24 instead of 28 months clearly reduces the number of youngstock needed at the same rate. Read more about costs and rearing in Outsourcing of youngstock rearing?.
Replacement through buying in
Some farms do not rear at all and buy in-calf heifers instead. This saves space and work, but makes the farm dependent on the market and brings the risk of new diseases.
Reading the rate correctly
A low replacement rate is only good if the herd is healthy. If sick or infertile cows stay in the herd too long, the rate falls, but so does performance. That is why you should always look at the reasons cows leave.
Frequently asked questions
How do you calculate the replacement rate?
The number of heifers entering the herd per year divided by the average number of cows, times 100.
What is a good replacement rate?
Many farms are at 30 to 40 per cent. A lower rate means a longer productive life and lower rearing costs per litre of milk, as long as the culling is voluntary.
What is the difference between replacement rate and culling rate?
The replacement rate counts the new heifers, the culling rate counts the cows that leave. With a constant herd size, both are the same.
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