Healthy calves, better beef
Why preventing BRD at weaning pays off
By Ingrid L.B. Fernandes and Tara L. Felix
If you raise cattle for beef, you probably noticed that over the past eight years, the production of beef × dairy crossbred calves has grown dramatically. These calves are currently valued between $1,000 and $1,500, which contributes meaningfully to the profitability of dairy operations while serving as an important supply for the beef industry. In fact, beef × dairy calves now account for approximately 20% of all fed cattle in the U.S. and are no longer considered mere surplus from the dairy sector. No doubt, beef × dairy calves became an essential component of the current beef supply chain.
The sheer volume of these beef × dairy calves being raised to produce beef, necessitates a deeper understanding of how these calves develop and what challenges they might face throughout their lives. For example, because beef × dairy calves are raised similarly to purebred dairy calves, they might be susceptible to the same health issues.
One of the most damaging diseases in pre-weaned dairy calves is bovine respiratory disease, commonly called BRD. Calves born on dairy farms undergo stressful events very early in their life, including their frequent sale and relocation at only a few days of age, increasing their risk of developing BRD compared to calves reared in conventional beef calf systems.
The most common BRD pathogens take advantage of the fragility of the immune system during stressful periods to infect the calf, causing respiratory signs such as cough, nasal discharge, heavy breathing, fever, and lung consolidation. However, for the producer, lung consolidation can be challenging to diagnose because it is only truly identified using lung ultrasonography, but it is a more sensitive and reliable tool, often preferred in research settings over clinical signs alone.
With a segmented supply chain like the cattle industry, healthcare might be inconsistent. These inconsistencies may not have immediately apparent consequences but could potentially impact the next sector later in the chain. However, we know little about the lasting impacts of this disease in calves born on the dairies that will enter the beef chain.
With that in mind, Tara Felix and Melissa Cantor, faculty members in the Department of Animal Science at Penn State, designed a study to investigate the impacts of BRD on the lifecycle of beef × dairy cattle. To reflect the reality of the industry, 139 calves were sourced from two dairies, transported to a calf raiser at ~2 days of age, transported again to a grower facility at weaning (~2 months of age), and lastly, moved to the PDA livestock evaluation center feedlot at around 12 months of age.
To assess calf health, lung ultrasonography was conducted on all calves 4 days post-weaning to identify lung consolidation and diagnose calves with BRD or those healthy. Calves were identified as “BRD” if they had lung consolidation of ≥ 1cm2 in at least one lobe or as “healthy” if they did not have lung consolidation.
Thus, at 4 days post-weaning, calves were assigned to groups with 35 calves considered BRD positive and 104 calves considered healthy. These identifications separated the calves into “groups”, for data analysis only, throughout the trial.
Weights were monitored at key time points throughout the study, feedlot intake was recorded using the Growsafe monitoring system, and calves were followed until slaughter (~15 months of age). At slaughter, hot carcass weight (HCW), dressing percentage, 12th rib fat (BF), ribeye area (REA), marbling score, and yield grade (YG) data were collected on every calf.
Calves that had been identified as having BRD at 4 days post-weaning had reduced average daily gain (ADG) by nearly a third of a pound per day up to 2 weeks post-weaning (12 weeks of age) when compared to their healthy counterparts. However, BRD calves recovered and compensated for those early ADG losses by 8 months of age, such that by 8 months of age there was no difference in ADG between BRD and healthy cattle. Complete results from the growing phase of this study can be found in Fernandes et al., 2025.
During the disease process, the immune system will respond, causing inflammation, modifying metabolism and decreasing DMI, which may explain the initial negative consequences on growth performance. Considering that calves were not treated for BRD at diagnosis, these data suggest that young calves might have an innate ability to overcome the disease insult over time.
During the feedlot period (the final ~ 160 days before slaughter), cattle growth performance did not differ between cattle that had been identified as having BRD or healthy at 4 days post-weaning. Similarly, there were no differences in many of the carcass traits, including HCW, dressing percentage, REA, BF and YG. However, marbling score at slaughter was reduced in cattle that had BRD at 4 days post-weaning compared to those that were healthy.
The reduction in marbling score was carried over to the carcass quality grade. Cattle with BRD at weaning tended to have a greater percentage of carcasses that graded Select (20.0%) and had a reduced percentage of carcasses that graded upper two-thirds Choice and Prime (14.3%), hitting less premium when compared to those cattle that were healthy at weaning (8.7 and 33.7%, respectively).
It is important to notice that the reduction in marbling score observed in cattle with BRD in our study may be associated with the fact that one of the most critical periods for intramuscular adipogenesis has been suggested to occur between the late fetal stages up to approximately 250 days of age in beef cattle. During this time, intramuscular adipogenesis is largely going through the process of hyperplasia, which is increasing the number of fat cells within the muscle, and this period is often referred to as “the marbling window.” After 250 days of age, adipocyte hypertrophy, which is the increase in the volume of fat cells present in the muscle, replaces hyperplasia.
In conventional beef cattle operations, calves remain with the dam for 180 to 200 days of life. Thus, most attempts to modify the marbling window have been conducted through early weaning systems or through early grain delivery programs (i.e. creep feeding). Our data suggests that perhaps adipogenesis can be impacted even earlier.
In our study, the growth insult from BRD diagnosed at weaning took place between 60 and 83 days of age. Therefore, we hypothesize that BRD at weaning reduced the number of fat cells within the muscle, and this impact was observed as reduced marbling in the carcass at slaughter 400 days later. This matters because over 70% of producers sell cattle in systems where the quality grade is part of the cattle price calculation. Therefore, producers purchasing beef × dairy progeny may be unknowingly purchasing cattle that will be discounted at the packer.
While the calves were able to compensate for the growth setbacks observed, the reduction in marbling observed at slaughter from animals with BRD at weaning suggests the need to ensure animal health throughout the whole chain of these crossbred calves to optimize marbling deposition, beef quality and profitability.
Fernandes is a PHD student and Felix is an associate professor and Extension beef cattle specialist, both in the Department of Animal Science at Pennsylvania State University.
