Prevalence and consequence of subacute ruminal acidosis in Polish dairy herds
Subacute ruminal acidosis (SARA) is one of the most important metabolic disorders in intensive dairy herds that occurs during early and mid‐lactation and affects rumen fermentation, animal welfare, productivity and farm profitability (Colman et al., 2013). Nutrient density and energy of the diets have to be increased by feeding high concentrates, including rapidly fermentable carbohydrates. However, these diets may cause a depression of ruminal pH due to the accumulation of volatile fatty acids (VFA) and cause occurrence of SARA (Plaizier et al., 2009). Several studies have investigated the aetiology and pathophysiology of these metabolic diseases; however, SARA syndrome is still not well defined (Danscher et al., 2015). SARA is traditionally characterized by a low rumen pH, that is below 5.8 for 3–5 h over a period of 24 h (Enemark, 2008). However, this definition of SARA may be less representative for field cases, because continuous measurement of ruminal pH is a practical and economical challenge under field condition (Danscher et al., 2015). There is no general agreement on the pH threshold that defines SARA; rumen pH may not even be highly correlated with the disease symptoms (Bramley et al., 2008). According to Nordlund and Garrett (1994), SARA can often affect the fermentation profile by an increase in the total concentration of VFA and acetic to propionic acid ratio and that has been shifted towards propionic and butyric acids. Morgante et al. (2007) suggested that valeric acid could be a potential biomarker of SARA, but more studies are required to detect and define the role of this acid.
There are many factors that can increase the possibility of occurrence of SARA in dairy farms and in particular in the intensive production. Morgante et al. (2007) investigated SARA in 10 Italian herds and found three herds with more than 33% of individuals with a pH <5.5 or less. Kleen et al. (2009) found an overall prevalence of 13.8% in 18 Dutch dairy herds with the stage of lactation having no detectable influence on SARA prevalence.
The incidence of SARA is difficult to determine; however, many results showed that the chemical composition of diet and its components is important to establish rumen metabolism and function and indirectly prevent this metabolic disease (Zebeli et al., 2008; Li et al., 2014). The optimal balance between physically effective NDF (peNDF) and rapidly degradable carbohydrates in the diet is difficult to achieve, but it is crucial for maintaining proper rumen fermentation and metabolic status, enhancing the longevity of dairy cows.
The aim of this study was to estimate the prevalence of SARA in Polish high‐yielding dairy herds. Also, the relationship between the chemical composition of the diet, feed particle size, ruminal pH and the occurrence of this metabolic disease and fermentation profile was determined.