I don't know the answer to this question but suspect that you can find it on the website for the Cornell College of Agriculture and Life Sciences: http://www.cals.cornell.edu/. They do a lot of work in this area.
There are a few ways that preg-checking can be done. 1. Sight: After the cow has been bred, you will start to see her sides grow as she gets further into pregnancy. By her third trimester she will look like a barrel with a head and four legs.... read more
ManyInterests, blood tests take too long to be analyzed and are too expensive to get done, especially if you have over 300 cows to preg-check. Rectal-palpation is the quickest, easiest, and cheapest way to tell if a cow (or even a mare!) is pregnant or not.