Listeria organisms grow well in poorly ensiled or spoiled feeds. Feeding silage can cause listeriosis or “circling disease.” To avoid problems, check the pH of suspect silage with pH strips or a handheld pH meter. “Any silage with pH of 5.5 or greater could have Listeria,” says Bill Seglar, nutritional sciences veterinarian with Pioneer Hi-Bred International. Always dispose of spoiled silage with a high pH to prevent it from getting into the ration.