Shell grit, the optimal source of calcium

The secret behind grit from marine shells is in the delayed availability of the calcium. Because of the size and structure of the grit it stays longer in the crop and arrives later in the stomach where the digestive acids dissolve it only slowly, thereby delaying the delivery of the calcium to the bloodstream. The grit we supply dissolves some 5 to 10 times slower than alternative sources of calcium like limestone or chalk. This has beneficial consequences where the bird’s calcium requirement is concerned. The delayed and more gradual availability of calcium leads to increased calcium levels in the blood. This increase takes place particularly at night, and therefore precisely when it most needed. The result is smoother, tougher and more visually attractive eggshells, and therefore fewer damaged and rejected eggs and less wastage. The bird will also continue to lay over a longer period.
Shell grit also contains far higher levels of beneficial minerals and metals than limestone or chalk. The coarse structure of shell grit allows the birds to selectively take up the nutrients in line with their calcium requirements. In this way shell grit can prevent overfeeding. This has beneficial effects on feed conversion, particularly towards the end of the laying period. Shell grit also has a specific action in preventing and combating any weakening of the bone structure. Its coarse structure also has beneficial effects in helping the poultry feed to run more freely and prevents differential settlement of the various feed components.

Eggshell formation

The production of a single egg requires the deposition of around 2.5 grams of calcium in the shell. This calcium requirement is provided from the blood or from reserves in bone, and the daily requirement during egg production may be up to 100 times what is present in the blood at any time. The amount of calcium drawn from the bones depends on what is provided with the food and on the time of day. The egg shell is mainly produced during the night when no food is taken. Calcium extracted from the feed in the small intestine is stored in the bone reserve at times when it can not be used immediately in the production of eggshell. During the night when calcium is needed to form eggshell it is obtained from bone. These calcium reserves can be very quickly available. As the bird ages however the speed and efficiency of mobilisation of this calcium declines, as does the quantity that can be mobilised. This means that laying hens in particular can have problems with calcium levels during the night, with a decline in eggshell quality as a result.

Improved returns for poultry-keepers; an overview of the benefits of shell grit:

  • Delayed uptake by the bird, resulting in more optimal use of calcium.
  • An excellent source of calcium.
  • A 100% natural product, organically formed calcium carbonate.
  • Improved feed conversion.
  • Drier manure.
  • Contributes to optimal bird health.


Laying hens

The bones and blood of laying hens provide them with a reserve of calcium, but highly productive layers need supplementary calcium to prevent calcium shortages and the resulting problems. There is an important link between eggshell quality and the calcium source and the calcium content of the feed. Adding shell grit to the feed improves eggshell quality, nutrient uptake and laying rates.

Turkeys and broilers

Shell grit is also successfully used in this sector. Fast-growing birds need a tremendously strong skeletal system to bear their own weight. The calcium level in the blood must therefore remain optimal at all times. Shell grit with its slow solubility provides a steady calcium level, 24 hours a day, with no peaks and troughs. For the poultry keeper the constant calcium level means less bone breakage, improved feed conversion and healthier birds. In short, using shell grit means improved profitability.


“Oystergritmix a fair calcium source for laying hens and meat poultry” The bones and blood of the hen serve as a calcium stock which has to be replenished before the time of lay. High producing h [..]

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