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Nutrition and Eggshell Quality

Adequate consumption of calcium, phosphorus, trace minerals (e.g., zinc, magnesium, manganese, and copper), and vitamin D3 is essential for eggshell quality. Bioavailability (and solubility) of the minerals vary greatly among feed ingredients and should be considered when formulating diets.

The eggshell contains about 2 g calcium regardless of the laying hen's age or egg weight. Therefore, as the hens' age and the eggs become larger, the shell becomes thinner. At the same time, the hens' ability to absorb calcium from the intestines diminishes. There are therefore several strategies to improve eggshell quality in late lay:

  • feed a pre-lay diet,
  • formulate diets for observed feed consumption,
  • control egg weight,
  • increase the dietary content of calcium,
  • change the form of the calcium supplement,
  • increase the consumption of vitamin D3,
  • increase consumption of 25-hydroxy vitamin D3,
  • increase consumption of organic (chelated) trace minerals, and
  • replace part of the dietary salt (NaCl) with sodium bicarbonate (NaHCO3) during hot weather.

Feed a pre-lay diet
The pre-lay diet should contain about 2.5% calcium and is fed for 2 weeks prior to the first egg (but not before 15 weeks of age). This type of diet helps develop medullary bone, which is a type of bone found inside the long bones (e.g., inside the femur). Medullary bone acts as a source (or reservoir) of calcium at night for eggshell formation. A more highly developed medullary bone will help improve eggshell quality, especially late in lay. Feeding the pre-lay diet is an option before the flock starts egg production.

Formulate diets for observed feed consumption
The percentage concentration of nutrients in the diet should correlate with the observed feed consumption, such that the diet provides the recommended grams or milligrams of the individual nutrients. Recommended diet concentrations for selected feed consumption rates and ages are available for each Hy-Line variety in the Performance Standards Manual.

Control egg weight
As mentioned above, larger eggs have thinner shells, so a relatively smaller egg will have a better shell quality. Egg weight is influenced by several factors, including body weight (larger hens will lay larger eggs) and nutrition. Start controlling egg weight with nutrition when the egg is 2 to 3 g lighter than the desired egg weight. Once the egg weight is too great, it is all but impossible to make it smaller without adversely affecting egg production. Egg weight can be influenced by reducing the consumption of amino acids (reduce all the amino acids, not just methionine, to make a less expensive diet), linoleic acid, and oil in general.

Increase the dietary content of calcium
The hens' ability to absorb calcium from the diet diminishes with age, so the dietary calcium content should be increased with age. This is reflected in the nutrient recommendations. However, sometimes, higher or lower levels of calcium will result in good eggshell quality. The optimal calcium level may be different from that shown in the Performance Standard Manual, but usually very close. Although it is preferred to increase the dietary content of calcium through changes in diet formulation, top-dressing with a calcium source (e.g., CaCO3, marine shells, or oyster shells) can be effective. In this case, the calcium source can be distributed by hand directly into the feeders (on top of the feed) or it can be added to the hopper or feed container at the feed-distribution point inside the house.

Change the form of the calcium supplement
The form in which calcium is added to the diet can also improve eggshell quality. Hy-Line recommends that 65% of the added CaCO3 should have a mean particle size of 2 to 4 mm, while 35% of the added CaCO3 should have a mean particle size less than 2 mm. The lower solubility of the large-particle-size CaCO3 will ensure that there is calcium available in the intestines during the night hours, when the hens normally do not consume the calcium-rich feed. If large-particle-size CaCO3 or oyster shells are top-dressed onto the feed instead of mixing it directly into the feed, it is best to top-dress in the late afternoon a few hours before the lights are turned off. A midnight feeding may provide sufficient calcium during the night, such that large-particle-size CaCO3 may not be necessary to optimize eggshell quality, although it is still recommended.

Increase the consumption of vitamin D3
Vitamin D3 is involved in the regulation of calcium absorption from the intestines. Therefore, increasing the consumption of vitamin D3 (though the vitamin premix or drinking water) may increase shell quality. Although Vitamin D2 may be available for purchase, Vitamin D2 is not metabolized by poultry and, therefore, has no vitamin-D activity. Therefore, only vitamin D3 can be used in poultry feed.

Increase consumption of 25-hydroxy vitamin D3
The 25-hydroxy (25-OH) vitamin D3 helps improve calcium retention and may be given through the feed or drinking water according with the manufacturer's recommendations. The 25-OH vitamin D3 can be mixed into the feed (e.g., through the vitamin premix) or administered through the drinking water.

Increase consumption of organic (chelated) trace minerals
Consumption of organic zinc (Zn), manganese (Mn), and copper (Cu) has been shown to increase eggshell quality, especially in older layers. As a result, about 20 ppm each of Zn and Mn could be included in the trace mineral premix and an additional inclusion rate of organic Zn, Mn, and Cu could be administered in the feed during mid to late lay.

Replace part of the dietary salt (NaCl) with sodium bicarbonate (NaHCO3)
Under heat-stress conditions, the diet can be re-formulated with 20 to 30% of the sodium (Na) coming from sodium bicarbonate (NaHCO3). During heat stress, birds increase their respiration rate ('pant') to remove excess heat, which, in turn, affects the bicarbonate buffer system in the blood. Specifically, the equilibrium

CO2 + H2O ? H2CO3 ? HCO3- + H+

shifts towards the left, in effect removing HCO3- from the blood. A reduction in the blood concentration of HCO3- can adversely affect eggshell quality, because the HCO3- is used for eggshell formation (the calcium in the eggshell is in the form of CaCO3). Adding a dietary source of HCO3- in the form of NaHCO3 can therefore help improve eggshell quality in warm weather. It is important to maintain the overall dietary content of sodium by reducing the amount of salt (i.e., do not just add NaHCO3 without reducing the NaCl in the diet), because an increase in sodium consumption can cause wet manure. Also note, that when salt (NaCl) is partially removed from the diet, the dietary content of chloride (Cl) is lowered; therefore, make sure that the diet contains sufficient chloride to meet the birds' needs. The minimum recommendations for sodium and chloride are provided in the Nutrition Recommendations section.

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