Day 2: Progesterone in a Nutshell
Exhibit A: Progesterone curves (“What nonsense is this?” <— Don’t worry, that’s what I also thought at first).
The above 2 curves represent the results of my progesterone tests for Pearl during her previous 2 litters. As a recap, Fast Car Litter = Aston and Gimli (pka Roy), and Elites Litter = Darcy (pka Dan), Agatha, Rory (pka Lorelei), Chopper (pka Bruno), and Gryff (pka Lance). The highlighted data points (28 and 28.6 nmol/L) represent when we detected that ovulation had happened (within the last 12-24 hours).
Progesterone is a hormone (more info about it via link) that has a significant role in starting, maintaining, and terminating pregnancy (hopefully with the birth of live offspring). Breeders will run progesterone tests at the beginning of a dam’s heat cycle to figure out when she is fertile and ready to be bred. Timing is especially important for a successful breeding - swimmers don’t survive for all that long if they’re being shipped (fresh chilled), and they definitely don’t live for very long when thawed (from a frozen state). That means that breeders need to (attempt to) have a precise measurement of exactly when the dam ovulates (releases her ova) so that they can arrange for either a live breeding, or a semen shipment, to occur on the best day for breeding.
Okay, let’s start over from the very beginning…
How we test for progesterone levels? We do a quick blood draw and send the sample off to IDEXX for processing. At some veterinary clinics, they can have the results in as soon as 30 minutes, but I wait until first thing the next morning for results. I often aim to have my first test done at 7 or 8 days, and then every 2-3 days thereafter.
What do progesterone levels tell us? See here for a sheet that explains levels of progesterone pre-ovulation! nmol/L = metric = Canadian units, ng/L = imperial = American units! There are different timelines for different breeding approaches: live / side-by-side breeding, fresh chilled semen, or frozen shipped semen (referred to in the prior sheet as “AI”. Generally, breeders aim to have their girls bred starting 1-2 days AFTER ovulation occurs. Ovaries release the eggs in an “unripened” state, and it takes them a short period of time to ripen and be ready for fertilization.
What is the exact sign you’re looking for with these tests? I’m Canadian, so I look for a sharp increase in progesterone above 15-20 nmol/L, which is why I identified the jumps in progesterone to 28+nmol/L as confirmation of ovulation.
Why do ethical breeders typically do progesterone testing? Progesterone is important not only to determine when the best day for breeding is, but also to know when the puppies’ due dates are. Canine gestation is on average 63 days, and pregnancies that terminate more than 2 days early or late are at severe risk of complications (premature if early, and other complications if late) involving both the dam and pups. If a breeder knows approximately when ovulation is, they can make an educated decision as when to bring a dam in for veterinary intervention if a pregnancy isn’t going as planned. My priority is always the dog in front of me - the dam, before the unborn puppies, so all of this is to guarantee her safety and comfort.
What’s a reverse progesterone test and why do breeders do these? While progesterone goes up to indicate that ovulation is happening, it actually decreases when pups are ready to be born. A reverse progesterone test (done in the same way as a regular progesterone test) checks whether this drop in progesterone is happening - invaluable in determining whether a litter of puppies may be ready for a C-section. Typically, veterinarians look for <2ng/L or <10nmol/L as the “green light” to indicate that pups are ready to be born.
And of course, I’ll be going over each stage as I go through it with Pearl in the next week and a bit.
Cheers,
Jenny
*all above are my own views opinions.
