Investigating Herd Health Problems Series: Part 1

 Defining the problem

We’ve all experienced it at one point in time or another. If you own cattle, you’ve undoubtedly had cattle develop illness or die for some unknown reason. If you are a veterinarian, you’ve undoubtedly investigated such cases, and understand how frustrating they can be. These types of herd health issues can be challenging for the producer and veterinarian alike, and often require critical thinking about causation of disease and accurate implementation of diagnostic testing to resolve. Misunderstandings about causation of disease or decreased production, as well as misuse of diagnostic tests can lead to situations where resources are invested in improper solutions, no improvement in the overall situation, and frustration of the producer and their veterinarian.

In this article, we will discuss the importance of a systematic veterinary investigation into problems of morbidity (i.e. illness) and mortality (i.e. death) in cow-calf herds. Outbreak investigations often require time, resources, and effort by the veterinarian and the producer, but the information derived from the investigation can be extremely valuable to resolving current animal health problems, and preventing their reoccurrence.

The first challenge to investigating problems with cattle health or performance is defining the problem. The initial complaint from the producer may include a variety of observed events (e.g. illness, death, decreased reproductive rates, poor growth rates, etc.). Sorting through which of the observed events within a herd are related, or which issues may be secondary to an underlying issue (e.g. pneumonia in weaned calves due to immunosuppression from bovine viral diarrhea virus) helps determine which of the events is of most importance, and establish a uniform case definition. Creating as specific a definition of the problem as possible helps compare cases to non-cases, and helps quantify the scope and magnitude of the problem.

Examining historical cattle health and production data can help identify patterns in disease occurrence, as well as determining the magnitude of deviation from “normal” health and production in the herd. During an outbreak investigation, quantitative data (e.g. dates when disease was observed, age of animals, treatment dates, etc.), ante-mortem and post-mortem examinations, diagnostic tests results, interviews of people involved, and critical examination of the operation as a whole (i.e. nutrition, biosecurity, biocontainment, husbandry, etc.) all aid the veterinarian in defining the problem and establishing a case definition.

Clearly defining the problem and establishing a case definition during an outbreak investigation provides focus to the investigation. Often, problems in livestock production systems are multifactorial, with many contributing causes, and a multitude of observed effects. Tackling a dynamic, multifactorial problem can be difficult and disheartening to veterinarians and producers. Focusing the investigation on one problem at a time can help keep interventions manageable and economical for the producer, and provide starting points for addressing other issues.

It is important to understand that involving the veterinarian as early in the process as possible can help reduce the impact of the outbreak and hasten resolution of the issue. If the producer waits until the problem is severe, or until it has been going on for a while, investigation of factors that contributed to the onset of the problem becomes more difficult.

Investigating Herd Health Problems Series: Part 2 will be available June 7th, 2022