Progesterone Testing: How to Actually Time a Mating

Most failed matings aren't fertility problems. They're timing problems.

A bitch is only fertile for a few days in a three-week season, and the old rule about mating on days 11 and 13 is an average drawn from a population, not a prediction about your dog. Some bitches ovulate as early as day four or five, and some as late as day 26 or 28. If yours is at either end of that range, counting days will put you nowhere near the window.

Progesterone testing is a blood test that tracks the hormone rise leading up to ovulation. It's the most accurate method available for timing a mating, and for a first litter it's the difference between a plan and a hope.

Three events, not one

This is the part that catches people out, so it's worth getting straight before anything else.

The LH surge comes first. It's the trigger, and progesterone lifts off baseline at around 2.0–3.0 ng/mL (6.4–9.5 nmol/L) as it happens. Breeders often call this Day 0 and count forward from it.

Ovulation follows about two days later, with progesterone somewhere in the region of 5.0–12.0 ng/mL (15.9–38.2 nmol/L).

Then comes the part almost nobody mentions on the forums. A bitch ovulates immature eggs. They need roughly another two days before they can be fertilised, which is why the most fertile days sit several days after ovulation rather than on it.

So when someone tells you "she's ovulated, get her mated", they may well be two days early. Ovulation is a marker you count from, not a starting gun.

Check the units on your report

UK labs commonly report progesterone in nmol/L. Almost every American breeding video, chart and Facebook post uses ng/mL. Multiply ng/mL by about 3.18 to convert, so 5 ng/mL is roughly 16 nmol/L. A result of 16 looks alarming if you assume ng/mL, and is simply ovulation if your lab works in nmol/L.

Look at the unit printed on the report before you look at anything else.

Reading the numbers

Those bands are a guide rather than a rule. The exact figures shift depending on which analyser your vet uses, and a single result on its own tells you very little. The timing comes out of the rise across several tests, not out of any one number.

Starting, and keeping going

Most UK practices suggest starting around day 7 from the first signs of the season, meaning vulval swelling and bleeding. Day 5 is sensible if she's ovulated early before, or if you want a clean baseline on a maiden bitch you know nothing about.

Test every two to three days while she's flat, then move to every 24 to 48 hours once the number starts climbing. Four to seven tests across a season is typical.

The mistake that costs litters is stretching the gaps once she's moving. The surge and ovulation play out over a handful of days, and spacing tests too far apart is the most common way breeders miss the window. A four-day gap in the middle of the rise can take you from "not yet" to "too late" with nothing in between.

When to put her to the dog

How tight the window is depends entirely on what you're breeding with.

Natural mating is forgiving. Sperm from a healthy dog survive several days in the reproductive tract, so a mating a couple of days after ovulation, with a second 48 hours later, covers you comfortably.

Fresh-chilled semen survives around 24 to 48 hours, so you're looking at roughly two to three days after ovulation, often as a single insemination.

Frozen is unforgiving. Thawed sperm last about 12 to 24 hours, which puts insemination at around two to two and a half days after ovulation with very little room either side. If you're using frozen, progesterone testing isn't a nice-to-have.

Where to get it done

There are broadly two options. In-house rapid kits are semi-quantitative ELISA tests that work on a colour change and give a result in about half an hour. Laboratory tests use chemiluminescence or similar, and give a precise figure.

The rapid kits are fine for answering "has she surged yet". They're less useful when you're trying to place a single frozen insemination.

A quantitative result is what you want for anything precise, and if your practice sends samples away you may be waiting until the next day. Some dedicated breeding services run an analyser on site and can call you back within a couple of hours, seven days a week including bank holidays. Weekend access is worth checking before her season starts rather than during it, because ovulation doesn't wait until Monday.

Whichever route you take, use the same one all the way through. Different methods produce slightly different figures, and since you're reading a trend rather than a value, switching halfway through makes the earlier results useless.

Cost

Around £35 a test is a common starting price, with general practices often charging more. Three to five tests over a season is normal, so call it £100 to £250 depending on where you go and how closely you need to track her.

Against a stud fee, the fuel to get to the dog, a shipped semen unit, and a whole season gone, it's not really a decision.

The part people don't expect

Testing doesn't just help you get her in whelp. Gestation measured from ovulation is far more consistent than gestation measured from the tie, so knowing the ovulation date gives you a whelping date accurate to within a day or so instead of the vague 58-to-68-day spread you get from counting from the mating. It's a considerably better assessment of when she's likely to whelp than the mating date on its own.

For a breed that regularly needs a caesarean, or a maiden bitch you want to be sitting with, that's arguably worth as much as the timing itself.

What it won't tell you

It can't predict when she'll come into season. A test is a snapshot of the moment the blood was drawn, and it tells you whether she has or hasn't ovulated, nothing more.

It says nothing about whether the stud dog is fertile, whether she has an infection, or whether the mating worked. Vaginal cytology alongside it gives your vet a fuller picture, and her behaviour still tells you something. Progesterone is the best single tool, but it's still one tool.

Before her next season

Ring your vet now, not on day 9. Find out whether they test in-house or send away, what it costs, how quickly results come back, and what happens if the critical day lands on a Sunday. If the answers are unsatisfactory, find a fertility clinic that suits you while you've got time to choose.

General guidance for breeders, not a substitute for veterinary advice. Always work with your own vet on breeding decisions for your bitch.