The monitoring, prevention and treatment of sub-acute ruminal acidosis (SARA): A review Jo ¨ rg M.D. Enemark * University of Copenhagen, Faculty of Life Sciences, Department of Large Animal Sciences, Medicine and Surgery, Hoejbakkegaard Alle’ 5, DK-6230 Taastru, Denmark Accepted 18 December 2007 Abstract Sub-acute ruminal acidosis (SARA) has become an increasing problem in well-managed, high yielding dairy herds and the monitoring of groups of cows for signs of the condition is now crucial. Rumenocentesis may be ethically questionable but the technique remains the most reliable means of diagnosing SARA. Continuous measurement of ruminal pH may however be possible in the future. Parameters reflecting the metabolic acidosis caused by SARA are also promising tools, and measurement of milk fat content may be useful in indi- vidual mid-lactation cows although it is less valuable for bulk tank milk samples. The prevention of SARA includes the establishment of feeding and management guidelines seeking to minimize rumen acidotic load. Regular monitoring may facilitate early recognition of the condition and limit economic losses. Some degree of SARA may however be inevitable and presents a challenge to the dairy industry as consumers become increasingly concerned about the welfare of production animals. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: SARA; Dairy cows; Management; Disease monitoring; Disease prevention Introduction Sub-acute ruminal acidosis (SARA), also known as chronic acidosis or sub-clinical rumen acidosis (SRA), is a well-recognised digestive disorder found particularly in well-managed dairy herds. Field studies in the United States have indicated that up to 19% of early lactation dairy cows as well as 26% of mid-lactation cows have SARA (Garret et al., 1997). Moreover, in one-third of the herds observed, 40% of all cows were found to have the condition. It has been estimated that the economic costs associated with SARA are US $500 million 1 to US$1 billion annually, with the cost per affected cow esti- mated to be US$1.12 per day. These losses are mainly the result of reduced milk production, decreased efficiency of milk production, premature culling and increased death loss. In a similar German/Dutch study, incidences of SARA in early and mid-lactation cows were found to be 11% and 18%, respectively (Kleen, 2004). It may therefore be appropriate to suggest that SARA is the most important nutritional disease of dairy cattle. This view is further sub- stantiated by the fact that the addition of buffers to total mixed rations (TMR) is almost standard in North Ameri- can dairy herds (Erdman, 1993). The challenge for dairy farmers, dairy nutritionists and bovine practitioners is to implement feeding management and husbandry practices to prevent SARA. To do so, however, demands that any ongoing SARA-problem can be recognized, which is not an easy task. This review deals with possible monitoring tools, and the treatment and prevention of SARA in dairy herds. 1090-0233/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2007.12.021 * Tel.: +45 35282833; fax: +45 35282838. E-mail address: jen@life.ku.dk 1 US$1 = approximately UK£0.50; €0.67, as at 22 February 2008. www.elsevier.com/locate/tvjl Available online at www.sciencedirect.com The Veterinary Journal 176 (2008) 32–43 The Veterinary Journal