Keep Her & Or Cull & Replace
Compares keep vs replace NPV
Every lactation you face the per-cow call: milk her again or sell her and bring in a heifer. This makes it on net present value — the present value of her remaining margin (by yield, parity and SCC) versus a replacement's lifetime margin minus the buy-in — and gives the keep/cull verdict and her break-even yield.
This cow vs a replacement
The path forks at today. Each branch stacks the discounted future margins and the eventual cull value; the replace branch first nets the heifer buy-in against the cull cash. The winning branch is bold.
Next: cull this cow and bring in a replacement: the heifer's higher lifetime margin (even after the ₹120,000 buy-in) is worth ₹365,497 more in today's money than keeping her. You would only keep her if her 305-day yield were above about 12,282 L — she is producing 7,000 L. Sell her before her condition or SCC erodes the cull value.
Margin/lactation = 305-d yield × milk price × (1 − SCC penalty) − feed cost. KEEP NPV = PV(remaining margins) + PV(cull value). REPLACE NPV = (cull received − heifer cost) + PV(heifer margins) + PV(heifer cull). Retention payoff = KEEP − REPLACE; keep if ≥ 0.
Runs entirely in your browser — nothing is uploaded.
Keep-or-cull — key facts
- Margin / lactation
- yield × price × (1 − SCC penalty) − feed
- Keep NPV
- PV(remaining margins) + PV(cull value)
- Replace NPV
- (cull − heifer cost) + PV(heifer margins+cull)
- Retention payoff
- keep NPV − replace NPV
- Decision
- keep if payoff ≥ 0, else cull
- Break-even yield
- where keep NPV = replace NPV
- Yield peak
- ≈ parity 3–4 (index 1.00)
- SCC penalty
- 0 / 3 / 8 / 15% by band
- Discount rate
- the dairy's cost of capital
- Privacy
- Runs in your browser; nothing uploaded
Parity yield index & SCC price-penalty bands
A cow's yield peaks around her third lactation then declines (index relative to peak = 1.00). A high somatic cell count cuts the milk price and the cow's margin. Representative planning figures.
| Lactation | Yield index | Note |
|---|---|---|
| 1st (heifer) | 0.78 | well past peak |
| 2nd lactation | 0.93 | declining |
| 3rd (peak) | 1.00 | near peak |
| 4th lactation | 0.98 | near peak |
| 5th lactation | 0.92 | declining |
| 6th lactation | 0.85 | declining |
| 7th+ lactation | 0.77 | well past peak |
| SCC band ('000/mL) | Price penalty |
|---|---|
| Healthy (<200k) | −0% |
| Elevated (200–400k) | −3% |
| High (400–750k) | −8% |
| Very high (>750k) | −15% |
Source: Cornell PRO-DAIRY & University of Wisconsin dairy replacement / retention-payoff NPV models; Penn State Extension "When to cull a dairy cow"; parity yield curves and SCC milk-quality schedules. Figures are representative planning presets.
Why "she still milks" is not the same as "keep her"
A cow earning a positive margin can still be the wrong cow to keep. The real question is not whether she pays her way, but whether she pays better than the heifer who could take her stall. That is a comparison of two futures: the margin she has left, set against the longer, usually larger margin stream of a replacement — net of the cash you must spend to buy that replacement now. Because the costs and benefits land in different years, the only fair way to compare them is to discount each future cash flow back to today.
This tool builds both futures. The keep branch discounts her remaining lactations' margins — driven by her 305-day yield, her parity (past peak, she gives less for the same feed) and her SCC (which docks the milk price) — and adds her eventual cull value. The replace branch nets the cull cash you collect now against the heifer's cost, then adds the present value of the heifer's lifetime margin and cull value. The difference is the retention payoff, and the break-even yield turns it into one number you can check against her milk records. Pair it with the Income-Over-Feed-Cost and the Herd Replacement-Rate tools to track the daily ration KPI and plan replacements herd-wide.
How to use it — 5 steps
- 1
Enter the current cow
Set her parity, 305-day yield, SCC, how many more lactations you'd keep her, and her cull value now.
- 2
Enter the replacement
Set the heifer's cost, expected 305-day yield, productive lifetime and eventual cull value.
- 3
Set the economics
Enter the milk price, feed and variable cost per lactation, and your discount rate.
- 4
Read the NPV fork
Compare the keep and replace branches and the retention payoff between them.
- 5
Act on the verdict
Keep her if the payoff is positive; cull and replace if negative — and check her break-even yield.
Frequently Asked Questions
Should I keep this dairy cow or cull and replace her?+
Keep her if the net present value of her remaining margin is higher than the net present value of replacing her — that is, if the retention payoff is positive. The keep NPV is the present value of her remaining lactations' margins plus her eventual cull value; the replace NPV is the cull cash you receive now minus the heifer's cost, plus the present value of the replacement's lifetime margin. The tool computes both and gives the verdict.
What is the retention payoff?+
The retention payoff is NPV(keep) − NPV(replace): how much more (or less) keeping the cow is worth in today's money than culling and replacing her. A positive payoff means keep; a negative payoff means cull. It is the standard dairy-replacement metric because it nets the cow's remaining value against the full cost and benefit of a replacement, not just her current milk.
What is the formula for a cow's margin per lactation?+
Margin = 305-day yield × milk price × (1 − SCC penalty) − feed and variable cost per lactation. Higher yield and a clean SCC raise the margin; a high somatic cell count cuts the effective milk price and so the margin. The tool discounts each lactation's margin back to today at your discount rate to build the keep and replace NPVs.
How does somatic cell count (SCC) affect the decision?+
A high SCC lowers the price you are paid for milk and signals mastitis risk. The tool applies a price penalty by band: 0% below 200,000 cells/mL, about 3% from 200–400k, 8% from 400–750k and 15% above 750k. That penalty reduces the kept cow's margin and tilts the decision toward culling, especially for an older cow already past her yield peak.
What is the break-even yield?+
It is the current cow's 305-day yield at which keeping and replacing are exactly equal in NPV. Above it, keep her; below it, cull. It turns the decision into a single number you can check against her milk records: if she is producing comfortably above the break-even yield she earns her keep, and if she has slipped below it a replacement pays.
Why does an older, lower-parity-index cow tend to fail the keep test?+
A cow peaks in yield around her third or fourth lactation and declines after, as shown in the parity yield index. An older cow therefore produces less milk for the same feed, so her margin per lactation falls, while a fresh heifer is climbing toward her peak. Combined with rising health and reproduction risk, that is why later-parity cows more often fail the keep-or-cull NPV test.
Does the replacement's higher yield always justify culling?+
Not always. A replacement heifer usually yields more, but you must pay her purchase or rearing cost now and wait for her margin to accrue, both of which the NPV discounts. If the current cow still has a strong, low-SCC lactation or two left and the heifer is expensive, keeping can win despite the lower yield. The tool weighs all of this, not just the yield gap.
What discount rate should I use for a cow?+
Use your dairy's cost of capital — often 6–10%. The discount rate matters because the replace path is more front-loaded with cost (buying the heifer) and back-loaded with benefit (her future margins). A higher discount rate makes those future heifer margins worth less today, which favours keeping the cow you already have; a lower rate favours replacing.
Is a cull cow's sale value part of the decision?+
Yes, on both sides. If you keep her, you still collect her cull value later (discounted), and if you replace her you collect it now. A high cull market raises the replace path's immediate cash and makes culling more attractive; a weak cull market favours keeping her milking. The tool includes the current cull value and the eventual cull value of both animals.
How is this different from a herd replacement-rate calculator?+
A herd replacement-rate tool works at the whole-herd level — what percentage of cows you replace each year. This tool makes the individual, per-animal decision for one specific cow using her own yield, parity, SCC and cull value. Use the herd tool to plan replacement budgets and this one to decide which particular cows to keep or cull.
Is a 7,000-litre cow worth keeping?+
It depends on her parity, SCC, milk price, feed cost and the cost and yield of the replacement. A 7,000-litre cow with a clean SCC and cheap feed can easily earn her keep, while the same yield with a high SCC and an inexpensive, high-yielding heifer available may not. Enter her figures and compare her keep NPV against the replace NPV and her break-even yield.
Can I keep a cow for just one more lactation?+
Yes — set the remaining lactations to one. That shortens her keep path so it must pay off in a single year against the replacement's longer stream. It is a common scenario for a borderline older cow you want to milk one more time before her cull value or condition declines; the NPV shows whether that single lactation still beats replacing her now.
How accurate are the parity and SCC tables?+
The parity yield index (peaking around lactation three) and the SCC price-penalty bands are representative figures of the magnitude reported in extension dairy-economics and milk-quality guidance. They are sensible defaults for the model; your own herd's lactation curves and your processor's exact SCC schedule will refine the answer. Replace the yield, price and cost inputs with your records for a farm-specific result.