The prevalence,
symptoms and economic impact of sub-acute ruminal acidosis in dairy herds
Anna Catharina Berge, DVM, MPVM, PhD.
Berge Veterinary Consulting BVBA
BergeVetConsulting.com
Sub-acute ruminal acidosis (SARA) is a metabolic disease in intensive dairy production systems. It involves reduction in rumen pH for prolonged periods due to accumulation of volatile fatty acids with changes in the microbial metabolism and nutrient degradation. The disease condition has mainly been attributed to high concentrate feeding that is common in high milk production herds. Clinical symptoms may involve decreased feed intake, milk fat depression, diarrhoea and laminitis, but in many cases it may simply be a sub-clinical depression in production. SARA was first described in feedlot cattle on high grain diets in the 1980s. A decade later it was described in 20% of cows in USA and similar estimates have been seen in continental Europe, indicating that it is a widely occurring condition in modern high-producing dairies.
Definition of SARA
SARA is a complex metabolic condition in the cow involving low ruminal pH for prolonged periods of time. SARA has been referred to as a pH drop under 5,5 for an extended time period (Plaizier, 2008). Since the pH is dependent on method and timing of measurement, there is no consensus threshold pH value that is definitive of disease and SARA is not simply an acidic rumen environment but also highly dependent on the rumen volatile fatty acids (VFA). Others would like to refer to SARA as ‘high-concentrate syndrome’ as it is not only a pH-dependent pathology but is also the result of changes in the microbial population secondary to the type of diet fed (Calsamiglia, 2010).
Prevalence of SARA
The prevalence of SARA is a measure of how many cows are affected at a particular time, whereas the incidence of SARA indicates how many new cases are occurring in a population. Prevalence is a function of the number of cows experiencing the disease and the length of the disease period. Therefore, an estimate of prevalence can either be due to a smaller number of cows with extended times of SARA or a larger number of cows with short times with SARA. The incidence of SARA has not been well described due to the difficulty in performing those kinds of studies. The diagnostic methods for SARA-associated signs in various studies include ruminoscentesis, indwelling pH meters and other approaches, which makes comparisons between studies difficult.
Several studies have been performed to determine the extent of SARA in dairy production. Studies on 15 dairies in Wisconsin in the United States indicated that 19% of early lactation dairy cows, as well as 26% of mid-lactation cows had SARA (Garret, 1997). Moreover, in one-third of the herds observed, 40% of all cows were found to have the condition. Another Wisconsin survey found that within 14 farms, 20.1% of early and peak lactation cows had SARA (Oetzel, 1999).
In a German and Dutch study, SARA in early- and mid-lactation cows was found to be 11% and 18%, respectively (Kleen, 2009), 18% in Italy (Cannizzo, 2009) and 11% in Ireland (O’Grady, 2008). Ireland has mainly pasture-based dairy production with modest productivity and this indicates that SARA is not simply a problem in intensive dairy production with high concentrate feeding. The high risk period has been described as early- and mid-lactation (Nordlund, 1995), however, the above mentioned studies did not find that SARA was influenced by stage of lactation.
Symptoms and consequences of SARA
Fermentation of feedstuffs in the rumen produces volatile fatty acids (VFA) and sometimes lactic acid. These acids may build up in cases where there is insufficient buffering capacity in the rumen leading to a reduction in the ruminal pH. Low ruminal pH may decrease feed intake and affect the microbial metabolism and nutrient degradation, particularly disturbing the fibrolytic bacteria metabolism. The clinical signs of SARA are subtle and often separated in time from the inciting event, thus making diagnosis difficult. Clinical symptoms linked to SARA include cyclic feeding patterns, milk fat depression, inflammation, laminitis, epistaxis and diarrhoea. Several symptoms of SARA, such as liver abscesses, rumenitis and laminitis may be associated with bacterial endotoxins (lipopolysaccharides) released from the rumen (Plaizier, 2008). SARA is considered to be a herd problem because the clinical signs are manifest in the herd rather than the individual (Enemark, 2009). Herd culling rates may be elevated and lower body condition scores may be present in SARA affected herds (Enemark, 2009; Kleen, 2009). It is, however, questioned whether SARA is a causative factor for various other metabolic conditions or simply an indicator of metabolic problems mediated by management (Kleen, 2010).
Economic impact of SARA
SARA has financial impact on production due to a drop in feed conversion efficiency, reduced milk production, decreased efficiency of milk production, premature culling and increased death loss. SARA has been linked to other metabolic conditions, such as all those affecting the transition cow, liver abscesses, rumenitis, inflammatory responses and laminitis. The impact of SARA was demonstrated by a field study on a large dairy farm in New York State that found that SARA reduced milk yield by 2.7 kg/day, milk fat production by 0.3% points and milk protein production by 0.12% points resulting in a financial loss of as much as $400 per cow per lactation (Plaizier, 2008). These costs excluded increased veterinary and culling costs. It has been estimated that the economic costs associated with SARA are US $500 million to US$1 billion annually, with the cost per affected cow estimated 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 (Enemark, 2009).
Summary
Sub-acute ruminal acidosis (SARA) can be described as an intensifying depression of ruminal pH for several hours several times per day (Kleen, 2010). SARA is widespread in modern-day dairies where cows are fed highly digestible diets. The extent of SARA in dairy production is under-estimated and not well determined due to the difficulties with disease definition and diagnosis. Whether SARA is indicative of a herd health problem or a disease complex per se remains debatable amongst the experts. Nevertheless, SARA may indicate sub-optimal management and production in a dairy and the economic impact of the metabolic condition is high.
Dr Joachim Kleen covered the Incidence and impact of SARA in dairy herds at the Dairy Solutions Symposium in Utrecht July 2010. Short papers from this meeting will be published on (website).
References
Calsamiglia, S., Ferret, A., Moya, D., Blanch, M., 2010 Modifying the rumen to reduce the risk of acidosis. Dairy Solutions Symposium, Rumen Health: A 360º Analysis, Utrecht, NL.
Cannizzo, C., 2009, Fermentative disturbs in dairy cow: subacute ruminal acidosis in field conditions and metabolic-inflammatory effects observed
http://paduaresearch.cab.unipd.it/1530/1/Tesi_dottorato_Chiara_Cannizzo.pdf
Enemark, J.M.D. 2009, The monitoring, prevention and treatment of sub-acute ruminal
acidosis (SARA): A review. Vet J. 176: 32–43
Garret, E.F., Nordlund, K.V., Goodger, W.J., Oetzel, G.R., 1997. A cross-sectional field study investigating the effect of periparturient dietary management on ruminal pH in early lactation dairy cows. J.Dairy Sci 80 (Suppl. 1), 169.
Kleen, J.L., Hooier, G.A., Rehage, J., Noordhuizen, J.P., 2009, Vet. Record, 164:681-3
Kleen, J.L., Cannizzo, C., 2010, Incidence and impact of SARA in dairy herds. Dairy Solutions Symposium, Rumen Health: A 360º Analysis , Utrecht, NL.
Nordlund, K.V., Garrett, E.F., Oetzel, G.R., 1995. Herd-based rumenocentesis: a clinical approach to the diagnosis of subacute rumen acidosis. Compendium for continuing education for the practicing veterinarian. Food Animals 17, s48–s56.
O’Grady, L., Doherty, M.L., Mulligan, F.J., 2008, Sub-acute ruminal acidosis (SARA) in grazing Irish dairy cows. The Veterinary Journal 176:44-49
Oetzel, G.R., Nordlund, K.V., Garett, E.F., 1999. Effect of ruminal pH and stage of lactation on ruminal lactate concentration in dairy cows. Journal of Dairy Science 82 (Suppl. 1), P35.
Plaizier, J.C, Krause, D.O., Gozho, G.N., McBride, B.W., 2008 Subacute ruminal acidosis in dairy cows: The physiological causes, incidence and consequences. / The Veterinary Journal 176 : 21–31
Anna Catharina Berge, DVM, MPVM, PhD.
Berge Veterinary Consulting BVBA
BergeVetConsulting.com
Sub-acute ruminal acidosis (SARA) is a metabolic disease in intensive dairy production systems. It involves reduction in rumen pH for prolonged periods due to accumulation of volatile fatty acids with changes in the microbial metabolism and nutrient degradation. The disease condition has mainly been attributed to high concentrate feeding that is common in high milk production herds. Clinical symptoms may involve decreased feed intake, milk fat depression, diarrhoea and laminitis, but in many cases it may simply be a sub-clinical depression in production. SARA was first described in feedlot cattle on high grain diets in the 1980s. A decade later it was described in 20% of cows in USA and similar estimates have been seen in continental Europe, indicating that it is a widely occurring condition in modern high-producing dairies.
Definition of SARA
SARA is a complex metabolic condition in the cow involving low ruminal pH for prolonged periods of time. SARA has been referred to as a pH drop under 5,5 for an extended time period (Plaizier, 2008). Since the pH is dependent on method and timing of measurement, there is no consensus threshold pH value that is definitive of disease and SARA is not simply an acidic rumen environment but also highly dependent on the rumen volatile fatty acids (VFA). Others would like to refer to SARA as ‘high-concentrate syndrome’ as it is not only a pH-dependent pathology but is also the result of changes in the microbial population secondary to the type of diet fed (Calsamiglia, 2010).
Prevalence of SARA
The prevalence of SARA is a measure of how many cows are affected at a particular time, whereas the incidence of SARA indicates how many new cases are occurring in a population. Prevalence is a function of the number of cows experiencing the disease and the length of the disease period. Therefore, an estimate of prevalence can either be due to a smaller number of cows with extended times of SARA or a larger number of cows with short times with SARA. The incidence of SARA has not been well described due to the difficulty in performing those kinds of studies. The diagnostic methods for SARA-associated signs in various studies include ruminoscentesis, indwelling pH meters and other approaches, which makes comparisons between studies difficult.
Several studies have been performed to determine the extent of SARA in dairy production. Studies on 15 dairies in Wisconsin in the United States indicated that 19% of early lactation dairy cows, as well as 26% of mid-lactation cows had SARA (Garret, 1997). Moreover, in one-third of the herds observed, 40% of all cows were found to have the condition. Another Wisconsin survey found that within 14 farms, 20.1% of early and peak lactation cows had SARA (Oetzel, 1999).
In a German and Dutch study, SARA in early- and mid-lactation cows was found to be 11% and 18%, respectively (Kleen, 2009), 18% in Italy (Cannizzo, 2009) and 11% in Ireland (O’Grady, 2008). Ireland has mainly pasture-based dairy production with modest productivity and this indicates that SARA is not simply a problem in intensive dairy production with high concentrate feeding. The high risk period has been described as early- and mid-lactation (Nordlund, 1995), however, the above mentioned studies did not find that SARA was influenced by stage of lactation.
Symptoms and consequences of SARA
Fermentation of feedstuffs in the rumen produces volatile fatty acids (VFA) and sometimes lactic acid. These acids may build up in cases where there is insufficient buffering capacity in the rumen leading to a reduction in the ruminal pH. Low ruminal pH may decrease feed intake and affect the microbial metabolism and nutrient degradation, particularly disturbing the fibrolytic bacteria metabolism. The clinical signs of SARA are subtle and often separated in time from the inciting event, thus making diagnosis difficult. Clinical symptoms linked to SARA include cyclic feeding patterns, milk fat depression, inflammation, laminitis, epistaxis and diarrhoea. Several symptoms of SARA, such as liver abscesses, rumenitis and laminitis may be associated with bacterial endotoxins (lipopolysaccharides) released from the rumen (Plaizier, 2008). SARA is considered to be a herd problem because the clinical signs are manifest in the herd rather than the individual (Enemark, 2009). Herd culling rates may be elevated and lower body condition scores may be present in SARA affected herds (Enemark, 2009; Kleen, 2009). It is, however, questioned whether SARA is a causative factor for various other metabolic conditions or simply an indicator of metabolic problems mediated by management (Kleen, 2010).
Economic impact of SARA
SARA has financial impact on production due to a drop in feed conversion efficiency, reduced milk production, decreased efficiency of milk production, premature culling and increased death loss. SARA has been linked to other metabolic conditions, such as all those affecting the transition cow, liver abscesses, rumenitis, inflammatory responses and laminitis. The impact of SARA was demonstrated by a field study on a large dairy farm in New York State that found that SARA reduced milk yield by 2.7 kg/day, milk fat production by 0.3% points and milk protein production by 0.12% points resulting in a financial loss of as much as $400 per cow per lactation (Plaizier, 2008). These costs excluded increased veterinary and culling costs. It has been estimated that the economic costs associated with SARA are US $500 million to US$1 billion annually, with the cost per affected cow estimated 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 (Enemark, 2009).
Summary
Sub-acute ruminal acidosis (SARA) can be described as an intensifying depression of ruminal pH for several hours several times per day (Kleen, 2010). SARA is widespread in modern-day dairies where cows are fed highly digestible diets. The extent of SARA in dairy production is under-estimated and not well determined due to the difficulties with disease definition and diagnosis. Whether SARA is indicative of a herd health problem or a disease complex per se remains debatable amongst the experts. Nevertheless, SARA may indicate sub-optimal management and production in a dairy and the economic impact of the metabolic condition is high.
Dr Joachim Kleen covered the Incidence and impact of SARA in dairy herds at the Dairy Solutions Symposium in Utrecht July 2010. Short papers from this meeting will be published on (website).
References
Calsamiglia, S., Ferret, A., Moya, D., Blanch, M., 2010 Modifying the rumen to reduce the risk of acidosis. Dairy Solutions Symposium, Rumen Health: A 360º Analysis, Utrecht, NL.
Cannizzo, C., 2009, Fermentative disturbs in dairy cow: subacute ruminal acidosis in field conditions and metabolic-inflammatory effects observed
http://paduaresearch.cab.unipd.it/1530/1/Tesi_dottorato_Chiara_Cannizzo.pdf
Enemark, J.M.D. 2009, The monitoring, prevention and treatment of sub-acute ruminal
acidosis (SARA): A review. Vet J. 176: 32–43
Garret, E.F., Nordlund, K.V., Goodger, W.J., Oetzel, G.R., 1997. A cross-sectional field study investigating the effect of periparturient dietary management on ruminal pH in early lactation dairy cows. J.Dairy Sci 80 (Suppl. 1), 169.
Kleen, J.L., Hooier, G.A., Rehage, J., Noordhuizen, J.P., 2009, Vet. Record, 164:681-3
Kleen, J.L., Cannizzo, C., 2010, Incidence and impact of SARA in dairy herds. Dairy Solutions Symposium, Rumen Health: A 360º Analysis , Utrecht, NL.
Nordlund, K.V., Garrett, E.F., Oetzel, G.R., 1995. Herd-based rumenocentesis: a clinical approach to the diagnosis of subacute rumen acidosis. Compendium for continuing education for the practicing veterinarian. Food Animals 17, s48–s56.
O’Grady, L., Doherty, M.L., Mulligan, F.J., 2008, Sub-acute ruminal acidosis (SARA) in grazing Irish dairy cows. The Veterinary Journal 176:44-49
Oetzel, G.R., Nordlund, K.V., Garett, E.F., 1999. Effect of ruminal pH and stage of lactation on ruminal lactate concentration in dairy cows. Journal of Dairy Science 82 (Suppl. 1), P35.
Plaizier, J.C, Krause, D.O., Gozho, G.N., McBride, B.W., 2008 Subacute ruminal acidosis in dairy cows: The physiological causes, incidence and consequences. / The Veterinary Journal 176 : 21–31