Progesterone testing

In my last post I talked about the hormones oestrogen and progesterone and their affect/involvement in controlling the oestrus cycle.  About 2 days prior to ovulation a surge in the secretion of LH causes the ovarian cells to switch from secreting oestrogen to progesterone. Prior to this LH surge, progesterone levels are very low . On the same day of the LH surge, progesterone levels will start to rise, continuing to do so through to ovulation and beyond. Once the bitch has ovulated, progesterone levels can vary greatly so the important test is knowing exactly when the progesterone has passed the ovulation mark. Once it's passed, you can't accurately predict how long ago ovulation took place.

Knowing the day of ovulation allows you to maximise contact time between viable semen (which can remain viable in the bitch's uterus for 3-5 days) and fertile eggs.  Once ovulated, the eggs take approximately 48 hours to become fertile. They will then remain fertile for approximately another 48 hours. The normal recommendation for mating is therefore days 1 and 3 or 2 and 4 post-ovulation.

So, on average, the LH surge occurs on day 10 (where day 1 is the first day where bleeding is detected in the bitch), ovulation 2 days later on day 12 and mating on day 14 and 16 (2 and 4 days post ovulation).

As mentioned earlier, prior to ovulation, progesterone levels as very low (less then 2 nmol/l). When the levels of LH surge, progesterone levels will quickly rise to above 6 nmol/l. At the time of ovulation, levels will be around 15-20 nmol/l. By detecting the change in progesterone levels around the LH peak, the date of ovulation can be accurately identified. While the LH surge is on average around day 10, it can be as early as day 5 or as late as day 25, which is why it's usually advised to start testing about day 5-7. Depending on the results from the first test, the lab will advise when next to test (usually about 3 days later).

There are "off the shelf" or "in house" kits that many vets stock (like pre-mate) that test for progesterone levels. It's important to realise that while they can give you a quick result (within the hour), they are qualitative tests, and not quantitative and are unable to provide you with accurate results. These simple ELISA based tests use colour changes to predict the levels of progesterone in the blood, with a stronger colour changes indicating higher levels. Lots of people have used them and swear by them, but there are just as many stories about them not working, due to a number of contributing factors (age of test, temperature, subjective colour analysis etc.).

Personally, I would only recommend the laboratory quantitative tests - I don't see the point in spending roughly the same amount of money (about £30) for a test that is not as accurate.  This is the place I am going to use Croft Reproduction. The have staff working 24x7 and will phone you on the same day that the blood sample is received. Can't ask for better service than that :) There are some other labs that will do the same test like Cambridge Specialist Labs but they are only open Mon-Fri business hours which is frustrating if you need results over the weekend !

The cost with Croft Reproduction : £30 for the test, £20 for my vet to collect the blood sample and £5 postage (£55).

I'm hoping that 2 tests will be enough, I really must learn how to take the blood myself - certainly doesn't look difficult and would save me £20 each time ! ;)