One Million Cattle Records Reveal Where the Fight Against Feedlot Respiratory Deaths Really Begins

A massive Australian study suggests the biggest risks for bovine respiratory disease are often established before cattle ever reach the feedlot.

A new analysis of more than one million Australian feedlot cattle is challenging the idea that bovine respiratory disease is mainly a problem to manage after animals arrive. Instead, the findings suggest that some of the strongest predictors of BRD-related death are already in place before cattle enter the feedlot, putting greater emphasis on source properties, pre-transport management and preventive care. The study, led by Adelaide University in partnership with Apiam Animal Health and Meat and Livestock Australia, examined health and production records from 1,040,253 cattle across three Australian feedlots between 2018 and 2024. Published in Preventive Veterinary Medicine, the research is described as the largest Australian study to date focused specifically on mortality associated with bovine respiratory disease.

Overall mortality in Australian feedlots remained low at less than 0.5%, but BRD stood out as a major infectious threat. Nearly 38% of the feedlot deaths recorded in the study were attributed to respiratory disease, reinforcing the importance of identifying cattle at risk before disease becomes established.

The Supplier May Tell You More Than You Think

One of the strongest findings involved the properties from which cattle originated. Animals coming from suppliers with a history of elevated BRD mortality were more than four times as likely to die from the disease as cattle sourced from lower-risk properties.That does not necessarily mean a supplier should be permanently labeled as high risk, but it does suggest that previous performance could become an important part of future risk assessment. Feedlots may be able to use supplier history to identify consignments that would benefit from additional preventive measures before or immediately after arrival. Darren Trott, director of Adelaide University's Australian Center for Antimicrobial Resistance Ecology and a senior author on the study, said many of the most important risk factors are present before feedlot entry. “Factors linked to the source property, the way cattle are managed before transport and how they are vaccinated can have a profound impact on survival,” Trott said.

He also cautioned that supplier risk should remain dynamic rather than fixed. As new health and performance information becomes available, risk classifications can be updated so changes in management or disease patterns are recognized rather than assuming that past outcomes will always predict the future.

How Cattle Get to the Feedlot Matters Too

The route cattle take before arriving at a feedlot was another important factor. Animals purchased through auction yards had a significantly greater risk of dying from BRD than cattle sourced directly from paddocks. That association fits with what veterinarians already understand about respiratory disease risk. Auction-market cattle may experience additional transport, handling, exposure to unfamiliar animals and commingling before reaching the feedlot, creating multiple opportunities for stress and pathogen exposure during a relatively short period of time.The study also showed that BRD mortality was heavily concentrated early in the feeding period. Approximately 69% of BRD deaths occurred during the first 60 days on feed, with the highest risk appearing around day 35 after arrival.

That timing reinforces the importance of prevention. By the time clinical disease is obvious, many of the conditions that contributed to illness may have been building for weeks.

Vaccinating Before the Stress May Make the Difference

One of the more encouraging findings involved vaccination. Cattle vaccinated against major respiratory pathogens before entering the feedlot had substantially lower BRD mortality than unvaccinated animals, with the strongest protective effect seen during the first two months on feed.

For principal author and Ph.D. candidate Gebremeskel Werid, the timing of vaccination appears to be especially important. “Vaccination for major respiratory diseases appears to be most beneficial when it occurs before cattle experience the stresses of transport and feedlot induction,” Werid said.

Giving cattle enough time to mount an immune response before they face transportation, commingling and feedlot induction may help reduce losses during the exact period when animals are most vulnerable. That makes pre-arrival vaccination more than a simple checklist item; it may be one of the most practical opportunities to alter disease risk before exposure and stress begin to accumulate.

Breed and Environment Also Played a Role

Researchers identified additional patterns involving genetics and environmental conditions. Bos indicus and crossbred cattle showed lower BRD mortality risks than temperate breeds, while seasonal differences in mortality were also observed. Some of those seasonal effects appeared to be connected to heat stress and changes in the risk profiles of source properties rather than season alone. The findings underscore the complexity of BRD, which rarely results from a single pathogen or management factor and instead emerges from interactions among immunity, stress, environment, genetics, transport and exposure.

That complexity is one reason broad preventive strategies may be more effective than waiting for individual animals to become sick and treating them one at a time.

BRD Prevention May Need to Start Beyond the Feedlot Gate

The implications extend beyond cattle survival. Preventing respiratory disease earlier could improve welfare and productivity while also reducing the need for antimicrobial treatment, an increasingly important consideration for antimicrobial stewardship.

Wayne Pitchford, director of Adelaide University's Davies Livestock Research Center, said the findings support a more coordinated approach across the beef production system rather than expecting feedlots to carry the entire responsibility for disease control.

“The greatest gains are likely to come from coordinated action between breeders, backgrounders, transport operators and feedlots to identify risk earlier and prevent disease before it takes hold,” Pitchford said.

That may be the study's most important message for veterinarians and producers. BRD may become clinically obvious after cattle enter a feedlot, but the biological and management conditions that determine which animals become seriously ill can develop long before arrival.

With more than one million cattle represented in the analysis, the data point toward a prevention strategy that starts earlier, uses supplier history more intelligently and places greater value on vaccination before the stresses of transport and feedlot induction begin.