• This site requires you to update your browser. Your browsing experience may be affected by not having the most up to date version.
    Please visit http://www.microsoft.com/windows/ie/ to upgrade.

  • JavaScript has been disabled in your browser. Please enable JavaScript to experience the full functionality of our website.

Separate feeding of calcium for poultry

  • Organisation University of Sydney, University of Nottingham
  • Full Report

Separate feeding of calcium for poultry

This series of studies investigated the presence and extent of an ‘appetite’ for an extra-dietary source of Ca in laying hens and established the optimum Ca and P concentrations and ratios of dietary Ca for optimum egg production and nutrient digestibility.

Hens eating in shed

The formation of hen bones and eggshells rely heavily on the ratio of calcium (Ca) and phosphorus (P), however, it is unclear what the optimum Ca:P ratio should be to maximise hen health, egg quality and production. 

Ca is present in many ingredients in feed, although sometimes a separate source of Ca, such as limestone, is needed to supplement hen diets because the hen might not be able to adequately utilise the Ca in the feed ingredients 


This project discovered that maximising dietary Ca (4.0-4.5%) results in greater egg and eggshell mass. Furthermore, higher shell thickness and Haugh units were stimulated if dietary Ca was matched by maximum dietary P (0.6-0.7%) at a ratio of 6:1Dietary Ca below 3% resulted in negative impacts on these factors and supplementation of the diet with a separate source of Ca did not prevent egg quality deterioration at low Ca levels. 

Despite this, providing limestone to supplement Ca did not improve nutrient digestibility and, subsequently, did not influence feed efficiency. 

Providing a separate source of Ca to hens on a low (1%) Ca diet was not sufficient to maintain egg production. Hens on a low Ca diet consumed greater amounts of limestonehowever, this was not uniform among the hens, which suggests that to some extent it may be a learned behaviour. Hens that were offered a diet with 3% or 4% Ca, plus limestone, had comparable productivity and egg quality.  

Want to see what an egg farm looks like? Take this interactive 360 degree tour to see how eggs are produced in Australia.

Free range farm with two people