I had a young cow abort today (7 months). I know it happens every once in awhile, I just haven't had it happen for a very long time. Any factors that may have contributed to this?? I only have a small herd- 25, so it is a big loss. Cows are well fed--corn silage, dry hay and Nutrena- NutreBeef Cattle mineral. Located in Pa. No vaccination program maybe that is my problem?