While it’s not new to the world of veterinary medicine, acute interstitial pneumonia (AIP) has become more and more of a problem in the past few years for cattle feeders. “There may be several reasons for this,” says Jerry Bohn, general manager at Pratt Feeders, Pratt, KS, “but the real cause and a viable solution to curing the disease are quite elusive.”

In fact, veterinarians with the Ontario Veterinary College at the University of Guelph in Ontario, Canada, noted in 1979 that clinicians and pathologists had observed cattle with the disease for several years. Still, however, little is known about the disease, other than that it tends to be fatal and doesn’t often respond to treatment.

According to Scott MacGregor, a consulting feedyard veterinarian from Idaho Falls, ID, the disease tends to show up most frequently during hot summer months. It also appears to show up in the high-quality, high-performing, big-eating cattle, Bohn says, adding that cattle with the best genetics appear to be the most susceptible.

What’s more, it tends to hit cattle at the end of the feeding period and affects animals singly, with no indication of an outbreak in the pen. “Other feedyard veterinarians have reported that it occurs far more frequently in heifers than steers,” says Larry Hollis, Kansas State University Extension veterinarian. “However, AIP has been observed in steers as well as heifers being fed in feedlots that do not use MGA to suppress estrus,” he explains.

While AIP is a feedyard disease, it’s a concern to cow-calf producers who retain ownership, Hollis says. Many times, those are the better-quality, better-doing cattle. Not only is it frustrating for the rancher to lose an animal close to the shipping date, but that’s a phone call the feedyard manager really hates to make.

Here are some points about the disease that feedlot personnel should be aware of:

  • AIP is a summer, hot-weather, possibly dust-oriented, problem.
  • Most cases of AIP are found during the last third of the feeding period.
  • The better the on-feed performance, the more AIP you’ll see.
  • Scientists feel AIP is caused from certain chemicals being produced in the rumen, traveling through the blood stream to the lungs and causing an allergic, shock-type of response.
  • Reducing stress when handling an affected animal is important because the animal is suffering from shock at the lung level.
  • An active bacterial infection is found in only about 20-25% of the AIP cases in a feedyard.
  • Therapy appears to be best achieved when the affected animal is left in its home pen, eliminating the stress of the trip to the hospital, and treated with Excenel® and dexamethazone.
  • Symptoms include spread-out feet; hard, open-mouth breathing, often with salivation; head extended in distress; and pen riders will sometimes notice emerald-green stools.

“On a more positive note,” Hollis says, “published data indicates that higher levels of Rumensin® may reduce the incidence of AIP. To date, however, AIP remains an enigma with expensive consequences that frustrates feedyard managers, veterinarians and cattle owners.”