Milk Persistency & How Well She Holds Her Yield
Tracks cows
Persistency % = this month ÷ last month × 100; the drop is the shortfall — enter two months' yield to get the persistency, the drop and a rating (excellent ≥92%, good ≥85%, poor below).
Check her lactation hold
Next: holding 93.3% is excellent — keep the ration and comfort steady so the lactation curve stays flat.
A normal lactation declines ~5–8% per month after peak; persistency below ~85% month-on-month often signals a feeding, health or management issue rather than natural decline.
Milk persistency — key facts
- Persistency
- this month ÷ last month × 100
- Monthly drop
- 100 − persistency %
- Excellent
- ≥ 92%
- Good
- 85% – 92%
- Poor
- below 85%
- Why it matters
- holds total lactation yield up
- Compare
- consecutive months, same cow
- Privacy
- Runs in your browser; nothing uploaded
A high peak only pays if she holds it
Every lactation rises to a peak and then declines — but how slowly it declines decides the total milk in the tank. Two cows can peak identically, yet the more persistent one out-milks the other over the whole lactation because she loses only a few percent a month instead of slumping. Persistency is one of the cleanest single measures of a productive, well-fed, healthy dairy cow.
This tool compares this month's yield with last month's to give the persistency percent, the drop and a rating — excellent at 92% or more, good above 85%, poor below. A sudden poor rating is your cue to check feed, heat stress and health before a whole lactation slips away. Pair it with the Fat-Corrected Milk and Lactation Yield tools to read the full picture.
Catch the slump early
A poor rating flags trouble before the lactation is lost.
Rank your cows
Find the cows that hold yield best.
Judge the ration
A fast drop often means the feed ran short.
Any milking animal
Cows, buffaloes, goats or ewes alike.
Frequently Asked Questions
How is milk persistency calculated?+
Persistency is this month's yield as a percentage of last month's: persistency % = this month ÷ last month × 100. A cow giving 540 L this month against 600 L last month has a persistency of 540 ÷ 600 × 100 = 90%. The drop is simply 100 minus that, so 10% here.
What is a good persistency figure?+
On this tool, 92% or higher is rated excellent, 85% to 92% is good, and below 85% is poor. A high-yielding dairy cow ideally loses only a few percent of yield a month after her peak. A sharp month-on-month fall flags a problem worth chasing before it costs a whole lactation.
Why does persistency matter?+
Total lactation yield depends as much on how well a cow holds her peak as on the peak itself. Two cows can peak the same, yet the more persistent one milks far more over 305 days because she declines slowly. Persistency is therefore one of the truest measures of a productive, well-managed dairy cow.
What causes poor persistency?+
A fast drop usually points to under-feeding for the yield, a ration that runs out of energy or protein, heat stress, a subclinical mastitis or other health knock, early pregnancy, or simply a cow well past her peak. Because the tool compares two real months, a sudden poor rating is a prompt to check feed and health first.
Is some decline normal?+
Yes — every lactation curve rises to a peak in early lactation and then declines, so a few percent drop each month is entirely normal and expected. What you are watching for is an unusually steep fall. A cow holding 90–95% month to month is doing well; one dropping to 80% needs a closer look.
Does this work for buffaloes and goats?+
Yes. Persistency is just a ratio of two yields, so it applies to any milking animal — cows, buffaloes, goats or sheep. The formula and the rating bands hold; only the typical yields differ. Compare the same animal month to month, or the same point of lactation across animals, for a fair read.
Which two months should I compare?+
Compare consecutive months of the same lactation — last month against this month — so the figure reflects the natural decline of the curve. Comparing across very different stages or after a feed change can mislead. For a herd view, run each cow and watch which ones decline fastest.
Can I use persistency to project total yield?+
Indirectly, yes — a consistent monthly persistency lets you extend the lactation curve and estimate the 305-day total, which is why persistency feeds lactation-yield projections. This tool gives you the single-month figure; for the full curve, pair it with a lactation yield calculator that uses persistency as an input.