Many days the farm vet will start his morning very early with what is called a "herd check" at a dairy. This has become common practice on today's dairy farms and happens normally every week or two weeks. The cows that have been bred are checked rectally, yes through the rear end, to see whether or not they are pregnant. The veterinarians are experts in the field of reproduction! They can detect the fetus/a pregnancy as early as 36 days old by palpation. When using an ultrasound, they can detect the pregnancy even earlier!
This procedure does not hurt the cows and most of them seem quite comfortable with the veterinarian. As the vet is walking along behind the cows this is a good opportunity for him or her to check for lameness issues, body condition, udder health, and general cow health. There will also be either the owner or an employee walking along at the head of the cows which enables them to get a good look at the eyes, ears and feed consumption. It is a great time to discuss issues on the dairy or just discuss the news! Here is a video showing the farm vet on a herd check.