We and the vets are struggling to answer why we are loosing calves this year, they are blonde and blonde cross cows/heifers with 3 different bulls used, some calves have been large but most are average sizes, the cows look well but not to over conditioned, they have all been bolused. Often calves are alive inside but then never take a breath once on the floor, a postmortem on one showed nothing unusual. We are just looking for any suggestions after many discussions of possible causes. Thank you.