Acidosis ruminal agudo

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The Veterinary Journal
The Veterinary Journal 176 (2009) 21–31 www.elsevier.com/locate/tvjl

Subacute ruminal acidosis in dairy cows: The physiological causes, incidence and consequences
J.C. Plaizier a,*, D.O. Krause a, G.N. Gozho b, B.W. McBride c
b a Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada R3T 2N2 Departmentof Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A8 c Department of Animal and Poultry Science, University of Guelph, Guelph, Canada N1G 2W1

Accepted 18 December 2007

Abstract During subacute ruminal acidosis (SARA) rumen pH is depressed for several hours per day due to accumulation of volatile fatty acids and insufficient rumen buffering. Surveys suggestedan incidence of SARA of between 19% and 26% in early and mid-lactation dairy cows. Causes of SARA include feeding excessive amounts of non-structural carbohydrates and highly fermentable forages, and insufficient dietary coarse fiber. Consequences of SARA include feed intake depression, reduced fiber digestion, milk fat depression, diarrhea, laminitis, liver abscesses, increased production of bacterialendotoxin and inflammation characterized by increases in acute phase proteins. The increase in endotoxin is similar among methods for SARA induction, but depends on the diet fed before induction. Increases in acute phase proteins vary among methods of SARA induction, even when the methods result in similar rumen pH depressions. This suggests that the inflammatory response might not be solely due tobacterial endotoxin in the rumen. Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Subacute ruminal acidosis; Dairy cows; Dairy herd health; Milk production

Introduction Milk yields of dairy cows in North America and Western Europe have increased substantially during recent years (Agriculture and Agri-Food Canada, 2005). As a result, the nutrient density of the diets fed to these cows hashad to be increased. This increase has been primarily achieved by feeding more concentrates and less forages. Feeding nutrient dense diets can result in a build up of organic acids in the rumen and reduced rumen buffering (Kleen et al., 2003; Stone, 2004; Rustomo et al., 2006a,b,c). The combination of these changes can lead to a depression of the rumen pH. When rumen pH is depressed for prolongedperiods each day, e.g. 3 h/day, subacute ruminal acidosis (SARA) occurs (Kleen et al., 2003; Stone, 2004; Gozho et al., 2005). This disease affects feed

intake, milk production, rumen microflora, rumen digestion, and can cause diarrhea, rumen mucosal damage, laminitis, inflammation, and liver abscesses in dairy cows (Nocek, 1997; Kleen et al., 2003; Stone, 2004; Alzahal et al., 2007). Severalexcellent reviews on SARA have been written in recent years (Kleen et al., 2003; Oetzel, 2003; Stone, 2004). This review will describe common causes and the incidence of SARA. Emphasis will be given on the effects of SARA on rumen microorganisms, bacterial immunogens and inflammation. Definition of SARA Current definitions of SARA are based on the pH of rumen fluid (Kleen et al., 2003; Oetzel, 2003; Stone,2004; Duffield et al., 2004). This pH can be measured after the collection of rumen fluid, either with a stomach tube or by rumenocentesis, or by placing in-dwelling pH probes in the rumen of rumen-fistulated cows (Duffield et al.,

*

Corresponding author. Tel.: +1 204 474 9500; fax: +1 204 474 7628. E-mail address: plaizier@ms.umanitoba.ca (J.C. Plaizier).

1090-0233/$ - see front matter Ó 2008Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2007.12.016

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J.C. Plaizier et al. / The Veterinary Journal 176 (2009) 21–31

2004). Continuous monitoring of rumen pH is advantageous due to its high diurnal variation (Keunen et al., 2002; Duffield et al., 2004). The technique used to measure rumen pH affects the pH values. There is disagreement as to a precise definition of SARA and...