*Dr. Chris Reinhardt is an extension feedlot specialist at Kansas State University, and Dr. Mike Hubbert is superintendent of the Clayton Livestock Research Center at New Mexico State University. To expedite answers to questions concerning this column, please direct inquiries to Feedstuffs, Bottom Line of Nutrition, 7900 International Dr., Suite 650, Bloomington, Minn. 55425, or email [email protected]
BECAUSE of the central role the liver plays in nutrient processing, any disturbance to liver function and capacity will potentially harm animal performance and efficiency.
Yet, remarkably, the presence of small or healed liver abscesses at harvest has been shown to have a negligible impact on animal performance. Conversely, the presence of multiple, large, active abscesses has been linked to a reduction in average daily gain of 0.18 lb. per day and a reduction in hot carcass weight of 20 lb. (Rezac et al., 2014).
Dry matter intake is reduced by 1.0 lb. per day in cattle with severe liver abscesses (Brink et al., 1990), and carcass quality may be reduced as well (Fox et al., 2009).
Active abscesses on the surface of the liver can result in the liver adhering to the inside of the carcass or bursting during removal of the organs during processing, both of which result in substantial carcass trim loss (Montgomery et al., 1985).
Liver abscess formation in cattle is initiated by a physical opening in the rumen epithelium (Nagaraja and Chengappa, 1998). The rumen is part of the portal-drained viscera, so any opening in the epithelium allows commensal rumen bacteria to infect the epithelium and to enter the portal blood.
Fusobacterium necrophorum, likely the primary causative agent of liver abscesses, is often associated or attached to the rumen epithelium, so any opening in the rumen wall will likely result in the exit of these bacteria from the rumen for passage to and filtration from the blood by the liver (Narayanan et al., 1997). Other organisms are often isolated from active liver abscesses, including Trueperella pyogenes. However, F. necrophorum is nearly always found in conjunction with these other bacteria (Nagaraja and Chengappa, 1998).
F. necrophorum produces an abundance of extracellular leukotoxin, allowing it to colonize the liver in the face of phagocytosis by leukocytes and Kupffer cells, creating a safe environment for bacteria also invading from the rumen. In addition, F. necrophorum, being an anaerobic lactate fermenter, may benefit from the simultaneous presence of the aerobic lactate producer T. pyogenes (Nagaraja et al., 1999), resulting in a synergistic co-infection.
The damage to the rumen epithelium is often the result of excessive organic acid production and, subsequently, low pH in the rumen. Liver abscesses are generally found in animals that are also demonstrating damaged rumen epithelium (Rezac et al., 2014), although this relationship is not one-to-one.
The incidence rate of total liver abscesses (including minor through severe cases) in U.S. feedlot cattle at harvest has increased from 12% in 2007 and 2008 to 16% in 2012 and 2013 (Elanco Animal Health internal data, 2014), although most of these animals were fed tylosin up through harvest. Kansas and Texas have the greatest incidence of severe liver abscesses, averaging 17% and 10%; the midwestern region averages 4%, and other regions remain intermediate.
Incidences of severe liver abscesses in calf-fed Holsteins in the High Plains of Texas and Kansas are 40% and 55%, respectively. Although liver abscess rates for Holsteins are typically greater than for beef breed steers, the rates for Holsteins in other regions of the U.S. are below 13% and are more in line with conventional beef animals. Studies are ongoing to investigate possible causes for this difference.
The incidence of liver abscesses generally increases with reduced roughage content in the finishing diet (Zinn and Plascencia, 1996). However, the form of the roughage can have an impact as well: Finely grinding the roughage source increases the amount of roughage that flows out of the rumen and decreases the amount of roughage remaining in the rumen to stimulate the rumen epithelium (Calderon-Cortes and Zinn, 1996).
Partial replacement of grain with corn milling byproduct feeds does not reduce the incidence of liver abscesses (Meyer et al., 2013). The fermentability of these ingredients and their fine particle size mean that they are not capable of stimulating any "roughage-like" response; they should be treated more like grain than like roughage. The fermentability of the grain source does not contribute greatly to liver abscess rates.
If the roughage level or form is "adequate," then an increased rate of starch digestion does not greatly affect liver abscess rates (Stock et al., 1987; Reinhardt et al., 1997). Conversely, if roughage is "inadequate," reduced starch fermentability does not reduce the liver abscess percentage (Loerch and Fluharty, 1998).
The duration of the acid insult from a high-grain diet may affect liver abscess rates. Backgrounding cattle on a forage-based diet prior to finishing on a high-grain diet reduces liver abscesses compared to feeding a grain-based diet throughout the feeding phase (Reinhardt et al., 1998; Checkley et al., 2005). F. necrophorum populations in the rumen increase three- to 10-fold in animals as they are switched from a forage-based diet to a grain-based diet (Nagaraja et al., 1999).
Feeding tylosin at 8-10 g per ton of the finishing diet continues to be an effective tool for controlling liver abscesses in feedlot cattle (Meyer et al., 2013) and is a common practice in U.S. feedlots. Tylosin likely influences liver abscess formation by suppressing populations of F. necrophorum and T. pyogenes in the rumen rather than in postruminal circulation or in the liver itself (Nagaraja et al., 1999).
Other antimicrobials are also effective and approved for control of liver abscesses (Rogers et al., 1995) but have not been widely used for that purpose.
Limonene, an extract of citrus, has been found to reduce ruminal F. necrophorum populations (Samii, 2014), and its inclusion in the diet may affect liver abscess rates (Meyer et al., 2007).
Vaccination against F. necrophorum reduced the incidence and severity of liver abscesses in challenge studies (Saginala et al., 1997), but field results have been equivocal (Jones et al., 2004; Fox et al., 2009). The level of the natural challenge may influence the efficacy of any intervention technology (Checkley et al., 2005).
The Bottom Line
Tylosin continues to be an effective means for reducing the incidence of liver abscesses. The efficacy of alternative methods to control liver abscesses may be improved after first reducing the baseline risk of infection.
Possible preventative dietary measures may include elevating the roughage level in the finishing diet, pulse-feeding a coarsely processed or long-stemmed roughage on a twice-weekly basis or extending the forage-based backgrounding phase prior to finishing.
Brink, D.R., S.R. Lowfy, R.A. Stock and J.C. Parrot. 1990. Severity of liver abscesses and efficiency of feed utilization of feedlot cattle. J. Anim. Sci. 68:1201-1207.
Calderon-Cortes, J.F., and R.A. Zinn. 1996. Influence of dietary forage level and forage coarseness of grind on growth performance and digestive function in feedlot steers. J. Anim. Sci. 74:2310-2316.
Checkley, S.L., E.D. Janzen, J.R. Campbell and J.J. McKinnon. 2005. Efficacy of vaccination against Fusobacterium necrophorum infection for control of liver abscesses and footrot in feedlot cattle in western Canada. Can. Vet. J. 46:1002-1007.
Fox, J.T., D.U. Thomson, N.N. Lindberg and K. Barling. 2009. A comparison of two vaccines to reduce liver abscesses in natural-fed beef cattle. Bov. Pract. 43:168-174.
Jones, G., H. Jayappa, B. Hunsaker, D. Sweeney, V. Rapp-Gabrielson, T. Wasmoen, T.G. Nagaraja, S. Swingle and M. Branine. 2004. Efficacy of an Arcanobacterium pyogenes-Fusobacterium necrophorum bacterin-toxoid as an aid in the prevention of liver abscesses in feedlot cattle. Bov. Pract. 38:36-44.
Loerch, S.C., and F.L. Fluharty. 1998. Effects of corn processing, dietary roughage level and timing of roughage inclusion on performance of feedlot steers. J. Anim. Sci. 76:681-685.
Meyer, N.F., G.E. Erickson, T.J. Klopfenstein, J.R. Benton, M.K. Luebbe and S.B. Laudert. 2013. Effects of monensin and tylosin in finishing diets containing corn wet distillers grains with solubles with differing corn processing methods. J. Anim. Sci. 91:2219-2228.
Meyer, N.F., G.E. Erickson, T.J. Klopfenstein, M.K. Luebbe, P. Williams and R. Losa. 2007. Effect of CRINA Ruminants AF, a mixture of essential oil compounds, on ruminal fermentation and digestibility. Nebraska Beef Reports, 1-1-2007, University of Nebraska, Lincoln.
Montgomery, T.H. 1985. The influence of liver abscesses on beef carcass yields. Special Technical Bulletin. West Texas State University, Canyon, Texas.
Nagaraja, T.G., and M.M. Chengappa. 1998. Liver abscesses in feedlot cattle: A review. J. Anim. Sci. 76:287-298.
Nagaraja, T.G., A.B. Beharka, M.M. Chengappa, L.H. Carroll, A.P. Raun, S.B. Laudert and J.C. Parrott. 1999. Bacterial flora of liver abscesses in feedlot cattle fed tylosin or no tylosin. J. Anim. Sci. 77:973-978.
Nagaraja, T.G., Y. Sun, N. Wallace, K.E. Kemp and C.J. Parrott. 1999. Effects of tylosin on concentrations of Fusobacterium necrophorum and fermentation products in the rumen of cattle fed a high-concentrate diet. Amer. J. Vet. Res. 60:1061-1065.
Reinhardt, C.D., R.T. Brandt Jr., K.C. Behnke, A.S. Freeman and T.P. Eck. 1997. Effect of steam-flaked sorghum grain density on performance, mill production rate and subacute acidosis in feedlot steers. J. Anim. Sci. 75:2852-2857.
Reinhardt, C.D., R.T. Brandt Jr., T.P. Eck and E.C. Titgemeyer. 1998. Performance, digestion and mastication efficiency of Holstein steers fed whole or processed corn in limit- or full-fed growing-finishing systems. J. Anim. Sci. 76:1778-1788.
Rezac, D.J., D.U. Thomson, S.J. Bartle, J.B. Osterstock, F.L. Prouty and C.D. Reinhardt. 2014. Prevalence, severity and relationships of lung lesions, liver abnormalities and rumen health scores measured at slaughter in beef cattle. J. Anim. Sci. Published online ahead of print April 21.
Rogers, J.A., M.E. Branine, C.R. Miller, M.I. Wray, S.J. Bartle, R.L. Preston, D.R. Gill, R.H. Pritchard, R.P. Stillborn and D.T. Bechtol. 1995. Effects of dietary virginiamycin on performance and liver abscess incidence in feedlot cattle. J. Anim. Sci. 73:9-20.
Saamii, S. 2014. Master's thesis. Kansas State University, Manhattan, Kan.
Saginala, S., T.G. Nagaraja, K.F. Lechtenberg, M.M. Chengappa, K.E. Kemp and P.M. Hine. 1997. Effect of Fusobacterium necrophorum leukotoxoid vaccine on susceptibility to experimentally induced liver abscesses in cattle. J. Anim. Sci. 75:1160-1166.
Stock, R.A., D.R. Brink, R.A. Britton, F.K. Goedeken, M.H. Smith, K.K. Kreikemeier, M.L. Bauer and K.K. Smith. 1987. Feeding combinations of high moisture corn and dry-rolled grain sorghum to finishing steers. J. Anim. Sci. 65:290-302.
Zinn, R.A., and A. Plascencia. 1996. Effects of forage level on the comparative feeding value of supplemental fat in growing-finishing diets for feedlot cattle. J. Anim. Sci. 74:1194-1201.