Use of PhytoMax© to counteract the negative effects of saline water on eggshell quality


In rural areas, springs, creeks and wells are often used as water sources for poultry farms.  Water coming from these sources, especially ground water, may be high in dissolved mineral salts, including sodium chloride.

Sodium chloride, NaCl, is essential for poultry, but it has been shown to have a severe adverse effect on shell quality when received in high concentrations through drinking water. NaCl reduces the breaking strength, shell thickness, shell weight, shell weight/egg weight and shell weight/unit surface, resulting in a higher incidence of cracked, broken and soft eggs. In breeders, saline water leads to a reduced numbers of settable eggs (eggs with an adequate shell quality for incubation) and to a lower hatchability.

Sensitivity to saline water

Sensitivity towards saline water depends on the age of the birds, breed, and individual factors of each hen or flock. Some animals are sensitive to concentrations as low as 200 mg NaCl/l drinking water, while others continue to lay good quality eggs at 2 g NaCl/litre.

When hens are exposed to saline water, the eggshell formation process is altered and, even if they are switched to water with less salinity or given any supplement for treatment, it takes at least 8 weeks to get back to normal.

With age, hens become more sensitive to saline water:

  • It is possible to prevent the negative effects of NaCl in pullets that have been exposed to saline water before sexual maturity, by administering a preventive treatment as will be discussed later or switching to water with less salinity.
  • Hens that are exposed to saline water at the beginning of the laying period often do not show shell defects until a much later stage, at 29 to 55 weeks of age (delayed effect). Even if after the administration of saline water they are switched to water with less salinity, the eggshell defects will appear anyway because the animals struggle to recover from the damage made by NaCl.
  • Hens that receive saline water during the laying peak rapidly show a significant worsening of shell quality, but still can recover after 8 weeks or more if switched to water with less salt.
  • Hens that are older than 40 weeks show a higher increase in the percentage of damaged eggs and can not fully recover from the damage produced by saline water.

Furthermore, different breeds of hens have different sensitivity to NaCl. In example, Isa Brown is more resistant than the cross between New Hampshire and White Leghorn. However, it must be taken in account that there is a lot of individual variation and one breed may show a high sensitivity in certain circumstances and be resistant in others.

Interference of NaCl with eggshell formation

The eggshell consists of 95% calcium carbonate, that is produced during eggshell formation from carbonate and calcium.


The negative effects of NaCl on eggshell formation occur possibly through the inhibition of the enzyme carbonic anhydrase and the transport of calcium into the shell gland, but the exact mechanism of action is not fully understood yet.

Sodium chloride interferes with the enzyme carbonic anhydrase

Carbonic anhydrase is an enzyme located in the shell gland that produces carbonate from water and carbon dioxide. This enzyme is zinc-dependent.


Whenever hens are exposed to high amounts of NaCl, the activity of carbonic anhydrase is reduced, and as a result there is less availability of bicarbonate in the shell gland.

Sodium chloride inhibits the transport of calcium to the shell gland

Calbindins are vitamin D-dependent calcium-binding proteins involved in the transport of calcium. They are present in many calcium-transporting tissues, including the intestines and the shell gland.

In hens exposed to saline water, the concentration of calbindins in the shell gland tissues is significantly reduced and, as a result, the uptake of calcium is impaired.


Administration of organic zinc to increase the activity of carbonic anhydrase and calbindins

As explained above, carbonic anhydrase is a zinc-dependent enzyme. It has been proven that the administration of zinc supplements significantly increases (40 to 70% more) the activity of this enzyme.

In hens exposed to saline water, zinc reduces the incidence of cracked, broken, soft and deformed eggs. The parameters related to eggshell strength, such as the breaking strength, shell thickness, shell weight, shell weight/egg weight and shell weight/unit surface, also improve after the administration of zinc supplements. Supplements based on organic zinc are more effective than those based on inorganic zinc, very likely due to the differences in availability.

Furthermore, the concentration of calbindins is also significantly increased (10-17%) after the administration of zinc supplements.

Use of PhytoMax© to counteract the negative effects of saline water on eggshell quality

PhytoMax© is a combination of vitamins, chelated calcium, microminerals and essential oils to be given through drinking water. It includes in its formula an effective concentration of organic zinc.

PhytoMax© is useful to...

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