"Sale barn is buyer beware."
That bears repeating.
Other than when we dispersed our entire herd, if a cow or heifer went to the salebarn, there was a REASON she wasn't staying. I guess not everyone has that perspective, but I never considered the salebarn as a place to purchase replacement cows/heifers. I figure, if they're there, there's something wrong with them, or they didn't make the breeder's cut... why do I wanna buy someone's culls?
Depending upon the strain of Mannheimia or Pasteurella present, disease & or death can come PDQ. Was involved with some vaccine trials back in the 1980s... a bolus of M.haemolytica was delivered into the lower airways by way of a catheter threaded down the trachea. Some of those calves inoculated with a 'hot' strain were dead within 18 hours.