The beef-on-dairy revolution has transformed the cattle industry in the U.S. In less than a decade, beef-on-dairy calves have evolved from virtually non-existent to making up nearly one-fifth of the U.S. fed beef supply.
The journey to the feedyard for those calves is quite different than that of their native beef pen mates. As this unique segment of the industry evolves, interest is growing in improving the systems that eventually bring those calves to market, from their dairy of origin to the packer.
In a recent I-29 Moo University webinar, Penn State University animal science graduate student Ingrid Fernandes presented results of her master’s degree research. The study examined the incidence of bovine respiratory disease (BRD) in beef-cross calves and its potential influence on fed beef performance.
Her presentation, “Long-Term Impacts of Early-life Bovine Respiratory Disease on Growth and Carcass Traits in Dairy Cross Cattle,” described the study that followed 143 calves from two Pennsylvania dairies from birth to harvest. The trial specifically focused on respiratory health and its long-term influence on animal performance.
Fernandes notes that according to 2017 USDA data, respiratory disease accounted for 32.7% of dairy calf mortality and 23% of death loss in beef calves. The same metric for beef-on-dairy calves is not currently known. She says dairy-style production systems, which vary considerably from a native beef calf’s upbringing, can leave calves vulnerable to BRD.
“A calf’s immune system develops gradually over its first eight months of life,” she says. “Everything that happens in that period can put them at risk of disease.”
Important stressors include castration, dehorning, transportation, dietary changes, dehydration, weaning, commingling and vaccination. Fernandes notes these stressors are often stacked together in dairy-style systems. Additionally, beef-on-dairy calves might make several ownership changes in their first eight months of life.
“Major BRD pathogens are commensal; they are part of the natural microbiota of the upper respiratory tract in cattle,” she explains. “Stressful events lead to compromised immune systems. This may create an imbalance in the microbiota, allowing the pathogens to travel to the lower respiratory tract, where they can cause inflammation, tissue damage and lung consolidation.”
Fernandes notes some calves with BRD exhibit obvious symptoms, while others display none. To positively diagnose BRD in the study, she and her team relied on thoracic ultrasonography at four days postweaning to detect lung consolidation.
Based on a number of criteria, including the size of lung consolidation area, they ultimately sorted calves in the first phase of the study into one group of 37 BRD-positive calves and another of 106 healthy controls. None of the calves in either group received any sort of treatment for BRD.
In terms of gain, an interesting phenomenon occurred. When evaluated up to 83 days of age, the calves with BRD suffered a loss in average daily gain (ADG) of about one-third pound per day. But when their performance was followed up to 238 days of age, they compensated for that lost gain and actually weighed slightly more than the controls by the end of that study period.
So, if they recovered, why worry? The answer: meat quality. When the same animals were observed in the second phase of the study, which followed them through the feedlot and ultimately harvest, some surprising findings emerged.
Compared to the controls, the BRD-affected cattle showed no significant difference in ADG, hot carcass weight, dressing percentage, ribeye area, 12th rib fat thickness or yield grade. But one area of vast difference did show up: marbling.
The calves with BRD had 7% lower marbling scores overall. In terms of quality grades, 34% of the healthy controls graded High Choice or Prime, while only 14% of the BRD calves achieved one of those grades. More specifically, the controls produced seven animals that graded Prime, while the BRD group had none. Cattle with BRD at weaning also tended to have 3.05 times greater odds of having a carcass graded Select than the control cattle that were healthy at weaning.
Fernades attributes these results to intramuscular adipogenesis, or the development of fat cells within the muscle. It’s a process that begins early in life, and that’s where a health challenge like BRD can make a difference.
“This is evidence that our management of beef-cross calves early in life can have lasting effects on their performance and ultimate value,” Fernades says. “It points to our need for communication between industry segments and calf-rearing practices that reduce stress and disease opportunism.”
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