Medium chain fatty acids and their impact on egg shell quality
The poultry industry is faced with increasing cost prices. This is mainly due to increased feed prices and/or changes in legislation (animal welfare, legislation on zoonoses like salmonella). As the genetic potential of both commercial layers and breeders is still improving, the production cycle can be prolonged in an economic way to compensate partly for these higher cost prices. Evaluation of field data, from the Benelux over the past 10 years, has shown that from the genetic
progress made in terms of egg production only 50% of this can be qualified as first grade hatching eggs. As production cycles are getting longer, the need to maintain or improve the egg quality after peak production will be higher.
With the ongoing tendencies to grow broilers and turkeys heavier and faster, extra attention is paid to skeleton development and skeleton strength by the breeding organisations. However it is well known from literature that breeding for better skeleton strength or better leg strength indirectly results in more second grade eggs. This can be explained by the fact that the
available calcium will either be used for the skeleton development or its maintenance, for the formation of the shell or in the muscular physiology. So changing emphasis in the breeding program can have indirect effects on other parameters. It should also be taken into account
that increasing the available calcium in the blood cannot be done infinitely as this would affect blood pH too strongly, resulting in death. An egg generally consists of three major parts: firstly, the shell, which is mainly calcium carbonate and about 2% of organic matrix. Secondly, there is albumen, which contains mostly proteins with antibacterial activity. Thirdly, there is also the yolk. The shell and the albumen have a nutritional and a protective value for the developing embryo
throughout the whole incubation process. The yolk has a nutritional value for the embryo in the later incubation period and post hatch. As the quality of the shell is not only determined
by the quantity of calcium in the shell but also by the structure of the shell, a lot of research is being undertaken to understand how the structure can be ameliorated. French research has indicated that 40% of the differences in shell quality can be explained by the organic matrix.
Data from breeding companies indicate that the calcium and the shell deposited around the eggs
(expressed as grams) as the hen ages does not decline but reaches a plateau after maximum egg mass production. However this means that ‘% of shell’ relative to the whole egg declines. Furthermore, as can be seen in Fig. 1, both the relative weight development of the albumen
and the shell are very much synchronised and that the relative weight development of the yolk is higher.
In the past, a lot of research in the breeder industry has been dedicated to searching for the right calcium source and the right granule size in order to improve calcium solubility and calcium absorption. Today these effects are well documented and generally implemented but still the
problem remains. The proper calcium source and the proper granule size should always be in line with the proper feeding strategy. Just increasing calcium and reducing phosphorous in
the feed in order to minimise shell problems will not result in the desired effect if, like in broiler
breeders, the feed is consumed within two hours and the absorbed calcium is not retained in the bones. The calcium cannot be used later on during the shell calcification process, but is directly excreted. Most central in the whole calcium metabolism is the blood and blood pH. It regulates the supply and demand of calcium from/to the different elements (Fig. 2). Another factor which has a significant impact on shell quality is the ‘buffering capacity’ of the hen to store the calcium, and to mobilise the calcium from the bones, in particular the medullary bone. This capacity is mainly determined during rearing and the first week of the production period.
Albumen and shell quality
Building a good shell is like building a good house with strong foundations. This foundation is the albumen and the surrounding...
Do you already have an account? Log in here