Liver abscess challenges are not new to feeder cattle. Processors have dealt with a reported liver abscess rate of 12% to 32% across the U.S. slaughtered beef population for years. Dairy genetic influence in the feed yard has often carried a black eye, though, due to an even higher prevalence of liver abscesses over native beef populations.
The cost of liver abscesses
A 2023 Michigan State University Extension report stated that cattle liver abscesses represent an economic loss to the U.S. beef industry of approximately $61.2 million a year. This does not include reduced carcass weight from the additional trimming required, reduced marbling deposition, and lower feedlot performance.
Dairy-beef cattle tend to face a higher prevalence of liver abscess scores due to how they are raised, which often involves starting on a higher concentrate diet at a younger age. A recent study at Michigan State took a closer look at the feedlot performance impact of abscesses. Cattle that had a more severe liver abscess score had a 0.2-pound reduction in average daily gain (ADG) compared to ones that had a slight or smaller abscess or none at all. This can be tied to the animal’s immune system, which requires energy to mount a response against the abscess, diverting energy away from growth or gain. Additionally challenging, cattle with liver abscesses don’t show clinical signs and are generally identified too late — typically at harvest.
A current feedlot study at Michigan State is looking at feeding a 20% or 40% corn silage ration to dairy-beef crosses to determine the effect of the diet on naturally mitigating liver abscess. Corn processing also plays a role that is being evaluated. The more readily fermentable starch from corn plays an important part in pH and gut health.
Complex role of bacteria
Recently, a collaborative effort between scientists from USDA’s Agricultural Research Service (ARS), Texas Tech University, Kansas State University, and West Texas A&M University looked at reliable and repeatable liver abscess models to learn the triggers.
The first model study, published in the Journal of Animal Science, is part of a series of studies conducted at the USDA-ARS Livestock Issues Research Unit in Lubbock, Texas.
Currently, the primary treatment to prevent liver abscesses in cattle has been in-feed antibiotics. However, this has come under more scrutiny, and alternatives to antibiotics are being evaluated.
“We are trying to ensure this model is effective and applicable to test nonantibiotic interventions in the future,” said Rand Broadway, a research scientist with the Livestock Issues Research Unit.
In the study, scientists worked with dairy and dairy-beef steers. They tested two diets (high grain-based and forage-based) and three bacteria commonly found in liver abscesses.
Researchers have theorized that when cattle are fed elevated grain, highly fermentable starch in the rumen is rapidly fermented by bacteria, causing a drop in rumen pH. This acidity causes damage to the rumen lining, allowing bacteria to travel out of the rumen and into the blood, reaching the liver and other organs where they can cause infection. The exact route these bacteria take to cause infection or injury to the liver is still unknown.
Scientists found bacteria associated with liver abscesses may not always originate from the rumen. An alternative route may be from the lower gastrointestinal tract. The research indicated in some cases, when these bacteria were not in the acidic rumen environment caused by a high-grain diet, no liver abscesses were detected. However, when they introduced bacteria directly to the rumen, they found the root of the liver abscesses and were able to isolate the bacteria from the infected sites.
This study confirms that an acidotic diet, combined with bacterial introduction in the rumen, can be used as a model to induce liver abscesses. Further research is being conducted to determine if the model can be used to evaluate new interventions of prevention.
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