Ostrea Oyster Flour is our most popular rumen buffer. It has an extremely complex honeycomb structure that provides all-day protection.

Ostrea’s unique physical and chemical characteristics make it an ideal rumen buffer. It has a large surface area, thanks to its complex honeycomb structure, that helps sustain a more consistent rumen pH. It also provides an excellent source of calcium.

Ostrea Oyster Shell and Seashell are taken from naturally occurring shell deposits in the North Sea. Both are rich in calcium carbonate, which is capable of binding with two molecules of Hydrogen, giving it twice the binding capacity of sodium bicarbonate. When molecular weights are considered Ostrea is 150% more effective.

Ostrea’s unique complex honeycomb structure means that only cows suffering from acid loading are targeted. This prevents over buffering to ensure the rumen pH stays within optimal levels. Its complex structure also provides long-term protection throughout the day giving you peace of mind.

Ostrea is extremely soluble meaning once it has finished buffering Ostrea becomes a rich source of calcium, essential minerals, and trace elements which are all available to the cow.



  • Sustained buffering capacity stabilises rumen pH in the optimum range between 6 & 7
  • Reduced risk of rumen acidosis, leading to improved performance & feed efficiency
  • Improved general health of high yielding dairy cows
  • Healthier hooves and reduced lameness
  • Improved Calcium : Phosphorous balance in feeding stuffs
  • Natural source of essential minerals & trace elements
  • Rich in Calcium
  • Good absorption
  • Add Ostrea® Seashell and Oyster Shell Flour as a complementary feeding supplement to their daily feed (see dosage).


  • Lactating Cows (Housed) - 100gms / head / day
  • Lactating Cows (Grazing) - 80gms / head / day
  • Calves & Young Stock - 50gms / head / day
  • Beef Cattle - 50gms / head / day


  • Available in 25kg & 1000kg bags


Ostrea Oyster Shell Ostrea Oyster Shell
Ash 99.44% Ash 99.44%
Calcium Carbonate 97.64% Calcium Carbonate 96.10%
Calcium 39% Calcium 44%
Phosphourous 10 mg/kg Phosphourous 12 mg/kg
Magnesium 3,900 mg/kg Magnesium 3,900 mg/k
Potassium 240 mg/kg Potassium 240 mg/kg
Sodium 4,600 mg/kg Sodium 4,600 mg/kg
Chloride 2,000 mg/kg Chloride 2,000 mg/kg
Sulphur 288 mg/kg Sulphur 288 mg/kg
Iron 2,800 mg/kg Iron 2,800 mg/kg
Manganese 180 mg/kg Manganese 180 mg/kg
Zinc 32 mg/kg Zinc 32 mg/kg
Cobalt 20 mg/kg Cobalt 20 mg/kg
Ostrea® Seashell and Oyster Shell Flours are a source of chalk derived from natural shell banks in the North Sea. The shells are washed, dried, heated, and then ground into a powder. Ostrea® is not just a rich source of calcium carbonate, but also contains a wealth of other minerals. Ostrea® is held in high regard by dairy farmers in Holland, Belgium, France, and the UK who have used the product as a rumen buffer for many years.


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Ostrea Oyster Flour

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