Determination of pregnancy date in Wistar rat - I need to know the morphological signs to determine the day of embryo (Jul/29/2008 )

Dear colleagues

I want to ask you if there is a way to evaluate morphologically the day of pregnancy in a rat. And I ll explain.
I m an animal technologist in Athens (Greece) and I have to provide to researchers embryos of day 16 till 18. Finding the plug is quite difficult and quite random. So I have established a technique in which I m weighting the rats before mating let them mate for the whole weekend and then I m weighting them again after 14 days and calculating the differences. If 10% or more is gained is considered pregnant. So I m guessing the possible age of the embryo. Is there any atlas from which I can calculate the day of the rat foetus? I only found some papers from scopus but they are too old and I can get only the abstracts. Any idea?

Dear Eparonis,

there is a very nice arlas of the developing rat brain from Altman here.

On the other hand, I have use as pregnancy test the presence of spermatozoan after vaginal wash and had an effectivity of 95%.
It take some time to get the practice to do it well and fast to not stress too much the animanls, but it worked in my case. I made caesarean operation at E18 an followed the weight curve as you mention, but I would not used it as diagnostic method. For my was useful as prove of loss of pregnancy...

I hope to have helped you,