When it comes to the diets of pre-fresh and post-fresh cows, Gary Oetzel, extension veterinarian at the University of Wisconsin, says you need to adopt a zero tolerance for butyric acid in ensiled forages. “Buying hay for pre- and post-fresh cows is generally much cheaper than the displaced abomasums, dead cows and loss of peak milk that occurs when these cows are fed ensiled forages containing butyric acid,” he says.