I had 70 head ultrasounded yesterday. It is very accurate and I have had it done for the past two years. For sexing the calves, it is best if it is done from 60-70 days. I did about 100 head last year, and I did all my recips. There were a few that were well over the 70 days pregnant, and the vet said that he could probably sex them but it would involve manipulating the fetus more, and I told him that I would find out what sex they were when they were born. I feel that the more the fetus is manipulated, the bigger chance you have of losing the pregnancy. They guy we used last year, was amazing, as his entire vet practice is only ultrasounding cows, so he had lots and lots of experience. I had some short bred heifers and I was not sure he would be able to tell if they were pregnant or not. I was amazed when he would say " this heifer is 27 days bred, no, I am going to say 26 days bred" When I checked the breeding date he was always right on. On the ones he sexed last year, he was 100% correct. As for the expected calving date, there was some variation to what he said, but this was probably due to other factors that affect gestation length. He was very close.
The vet yesterday could take a picture of any body part, and then calculate the length of pregnancy after we had checked all the cows and heifers. For example, he snapped pictures of the eye of the fetus, or maybe the entire body. By measuring the size of the eye or any other body part, the ultrasound machine calculated the age of the fetus. He said that he had found this to be extremely accurate regardless of the breed involved or the eventual birth weight of the calf. I guess that at these stages of life, fetus size is very similar regardless of breed or bloodlines involved. I have a list of his expected calving dates and I will see how accurate he was, at calving time next spring.
Ultrasound is also excellent for use on problem cows. I have an older donor cow that has probably been flushed too much and I have been having a hard time getting her to hold a pregnancy. The vet checked her yesterday, and was able to tell me that she has some damage to the wall of her uterus, which was probably why she was only staying pregnant part of the term. He said other than that, her reproductive tract looked good and she was cycling normally. She is supposed to be in heat in a few days and I am thinking I may try to pull some single embryos out of her and rest her over the winter. Normally, she would go to market, and that day will come, but she has produced over $100,000 of progeny and embryos, so I may go the extra mile with her.
