Most feedlot mortalities can accurately be diagnosed by feedlot health workers without the time, expense or risk of performing a detailed necropsy . However, some less common mortalities still should be investigated with a thorough necropsy.
Kansas State University veterinary researchers set out to compare the diagnostic accuracy of pre-necropsy mortality diagnoses by feedlot health personnel with those from a traditional necropsy.
Information pertaining to where an animal was found dead (home, hospital or chronic pen) was recorded. Feedlot health workers at a western Kansas feedyard were asked to determine the cause of death of 54 mortalities based on:
- Prior medical history,
- Treatment records,
- Personal knowledge and
- Location where the animal was found dead.
Meanwhile, the investigators, unaware of the pre-necropsy feedyard diagnoses, conducted a thorough necropsy on each animal and obtained digital images of lesions before determining the post-necropsy cause of death. The pre- and post-necropsy causes of death were grouped into several categories for data analysis and comparison.
The study found 100% agreement between the feedyard worker pre-necropsy diagnosis and the post-necropsy diagnosis for bovine respiratory disease (BRD) cases. They concluded that necropsy is not warranted on mortalities previously diagnosed and treated for BRD, and especially for cattle found dead in the hospital or chronic pens. Of the 25 BRD cases, 22 were found dead in the hospital or chronic pen, and 24 had a previous history of BRD treatment.
Bloat also had 100% agreement between pre- and post-necropsy cause of death. All study animals diagnosed as bloat mortalities were found dead in their home pen and had no history of medical treatment. Thus, necropsy of bloat mortalities isn’t warranted.
Injured cattle posed a unique situation in that they were classified pre-mortem as injured. The agreement between pre- and post-necropsy diagnoses was poor in injured animals.
Cattle with a traumatic injury often have multiple disease processes occurring simultaneously. Individuals conducting the necropsy likely don’t have an opportunity to observe an animal’s movement prior to necropsy, and assignment to a non-injury disease category is likely. The study results support that necropsy of mortalities with severe physical trauma and injury is unwarranted.
Atypical interstitial pneumonia (AIP) was under-reported by pre-necropsy determination of cause of death. Most AIP cases died in their home pen without receiving treatment. Because of AIP under-reporting, it’s suggested that animals found dead in their home pen without symptoms of bloat or BRD  treatment history should be necropsied.
Thus, a logical approach would be to necropsy only animals that don’t easily fall into the BRD, bloat or injury categories.
Scott B. Laudert, Ph.D., is a beef cattle technical consultant and former Kansas State University Extension livestock specialist based in Woodland Park, CO. He can be reached at 719-660-4473.