SARA in Dairy Cows

SARA in Dairy Cows

What is SARA?
SARA, or Subacute Ruminal Acidosis, is a prolonged and repeated period of abnormally low rumen pH.  Rumen pH fluctuates during any 24 hour period and is determined by the dynamic balance between the intake of fermentable carbohydrates, the production of volatile fatty acids (VFAs), the buffering capacity of the rumen and the rate of VFA absorption. Normal rumen pH is considered to be 5.8 and above. When pH drops below this for more than a few hours a day, a cow is considered to have SARA.

Caused by the Pressures of Modern Farming
Over recent years, the increasing milk yield and associated energy requirement of the modern dairy cow has led to challenges in achieving good nutritional management. Incorrect feeding of diets that are high in rapidly fermentable carbohydrates and low in fibre can lead to SARA.

Clinical Signs

  • Reduced or cyclic feed intakes
  • Decreased milk yield
  • Decreased  efficiency of milk production
  • Diarrhoea
  • Variable dung consistency
  • Regurgitated cud balls

SARA has also been associated with laminitis and subsequent hoof overgrowth, sole ulcers and sole abscesses.

Methods of Diagnosis

  • Diagnosed at the herd level
  • Milk recording data used to monitor fat:protein ratios of high risk groups
  • Measurement of individual butterfat levels and  fat:protein ratios
  • Regular body condition scoring
  • Rumen fill monitor feed intake scoring
  • Dung consistency scoring to assess the amount of undigested fibre present
  • Analysing rumen fluid samples taken directly from the rumens of at risk cows.

Prevention
SARA can be prevented by adhering to some basic rules. Correct transition feeding of pre-calvers will prepare the rumen for the lactating ration by increasing the surface area for VFA absorption and providing a healthy microbe population. Fermentable carbohydrate in the lactation ration should be balanced by long fibre of 5cm in length to promote saliva production and rumination (cows will tend to sort straw from the ration if it is poorly chopped) and dramatic changes in the ration and periods of feed deprivation should be avoided. Addition of dietary buffers such as sodium bicarbonate will help, and supplementing the diet with microbials such as yeasts help promote a healthy rumen flora.

Long Term Implications

Lameness can be a significant source of chronic pain and financial loss and generally does not appear until weeks or months after the episode of SARA. Repeated episodes of SARA will also lead to inflammation and damage in the rumen wall. This is painful and will cause reduced feed intakes. If the damage to the rumen wall is severe, bacteria will leak from the rumen into the circulation, leading to abscesses in the liver and the lungs and infections elsewhere in the body. Therefore farms with SARA will often have high rates of culling and unexplained deaths.

If you would like to discuss SARA with us, call 01746 713 911

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