Liver Abscesses in Feedlot Cattle: A Hidden Cost

By: Dr. Jacob Hagenmaier Production Animal Consultation

A“disease of healthy cattle”. This oxymoron has been used to describe liver abscesses and stems from the notion that a pen of cattle with no liver abscess prevalence at harvest were not challenged to perform at their maximum genetic potential. However, the liver is a major organ and responsible for multiple functions vital to life, such as glucose synthesis and detoxification of the blood via filtering of metabolic by-products. As such, abscessation has potential to negatively impact efficiency of growth and ultimately your bottom line.

Multiple review articles comprehensively summarize the research aimed to better understand liver abscess formation and potential mitigation strategies (Nagaraja and Chengappa, 1999; Nagaraja and Lechtenberg, 2007; Reinhardt and Hubbert, 2015). As a general overview, these lesions are believed to primarily occur following a bout of ruminal acidosis, typically associated with introduction to or variations in consumption of rapidly fermentable carbohydrates from diets high in concentrate. Sequelae of ruminal acidosis include rumenitis and focal impairments in the ruminal epithelium (gut wall). These impairments result in increased permeability of the gut wall and allow commensal, opportunistic ruminal bacteria to be absorbed into blood circulation and travel to the liver via the portal vein (the blood vessel draining the gastrointestinal tract). Although additional bacterial species such as Arcanobacterium pyogenes have been isolated from abscesses, Fusobacterium necrophorum is considered the primary etiologic pathogen, which is the same bacteria responsible for infectious bovine pododermatitis (foot rot) and necrotic laryngitis (diphtheria).

Liver abscesses are a multifactorial condition resulting from complex interactions among the three arms of the disease triad: the host, environment, and pathogen. Risk factors for liver abscesses include, but are not limited to, diet, gender (steers at higher risk than heifers), genetics (Holsteins at higher risk than beef breeds), age or immunocompetency, dry matter intake, and days on feed. Because of the multifactorial complexity of the disease, the severity can vary both within and across groups of cattle. A four-point scoring system has traditionally been used to categorize liver abscess severity and defines scores as: 0 – Normal liver, A- – one or two small abscesses, A – two to four well-organized abscesses, or A+ – one or more large, open abscesses with or without adhesions.

The negative effect on growth performance is inconsistent when considering smaller, less severe abscesses but can be profound with large, active abscesses. The economic impact of severely abscessed livers is three-fold: 1) loss value of liver due to condemnation (+/- additional viscera), 2) reduced live performance efficiency, and 3) carcass trim due to adhesions to the diaphragm and surrounding tissue, and contamination attributable to abscess rupture. A recent study conducted by researchers at West Texas A&M University (Herrick et al., 2018) evaluated the economic impact of liver abscesses in Holstein steers and reported carcasses with an open and adhered abscess had a gross carcass value of over $110 less than steers with a normal, edible liver. A separate report from 2010 (Brown and Lawrence, 2010) retrospectively evaluated the association of liver abnormalities on carcass grading on over 75,000 cattle and reported carcasses with severe liver abscesses were worth 3.8% less than carcasses from cattle with no liver abnormalities.

Unlike the other causes of feedlot morbidity, we do not visually recognize any clinical signs attributable to liver abscesses and the abscesses are typically only detected at harvest. A recent observational study (Herrick et al., 2018) evaluated over 130,000 livers from fed cattle and reported an abscess prevalence of 20.3%, which would rival the prevalence of bovine respiratory disease. In some cases, liver abscess formation near the caudal vena cava can cause embolus formation leading to other disease presentations such as embolic pneumonia and endocarditis.

To date, tylosin has demonstrated the most effectiveness for controlling liver abscesses in feedlot cattle. Vaccines have been approved for reducing the prevalence and severity of liver abscesses, however field studies supporting their effectiveness are lacking. Additional strategies to prevent and control the formation of liver abscesses should focus primarily on feeding and dietary management, with considerations given to the rate at which cattle are adapted to a high-concentrate diet and minimizing variations in feed delivery (over-feeding, under-feeding, time and number of feedings).

I’d challenge us all to think more broadly about liver abscesses and the potential implications of a disease that we do not visually observe until harvest.

References

Brown TR, Lawrence TE. Association of liver abnormalities with carcass grading performance and value. Journal of Animal Science 2010;88:4037-4043.

Herrick R. Experiments towards a greater understanding of the liver abscess complex in fed beef (Doctoral dissertation). 2018.

Herrick R, et al. 481 Association of liver abscess presence and severity with trim loss, harvest yield, carcass grading performance, lung lesions, and value of fed Holsteins. Journal of Animal Science 2018;96(S3):269.

Herrick R, et al. 484 Exploratory observational quan ti fi cation of liver abscess incidence, specific to region and cattle type, and their associations to viscera value and bacterial flora. Journal of Animal Science 2018;96(S3):270-271.

Nagaraja TG, Chengappa MM. Liver abscesses in feedlot cattle: A review. Journal of Animal Science 1998;76:287-298.

Nagaraja TG, Lechtenberg KF. Liver abscesses in feedlot cattle. Veterinary Clinics of North America: Food Animal Practice 2007;23:351-369.

Reinhardt CD, Hubbert ME. Control of liver abscesses in feedlot cattle: A review. The Professional Animal Scientist 2015;31:101-108.