Nutritional Influence on Egg Production:


Stable eggshell quality allows for a prolonged laying cycle By Dr. Stefan Hirtenlehner, Agromed


Abstract A major challenge in the egg producing industry is to increase the number of laid eggs per hen. Aside from genetic selection, producers can, to a certain extent, directly influence the performance of laying hens via management strategies, via different climate regimes or via the supply of a well-balanced feed. The goal to prolong the laying cycle is inevitably linked with the goal to stabilize the laying persistency at a high level, whilst maintaining eggshell stability over time. An optimized gut function together with a physiologically intact and healthy metabolism is a prerequisite to achieve these objectives. An improved gut function does not only contribute to prolongation of the laying cycle and counteracts deterioration of eggshell quality in older hens, but also has a beneficial impact on barn air quality and consequently improves a hen’s laying performance. Integration of lignocellulose and wood derived bioactive substances in a holistic feeding strategy represent a powerful tool to achieve financial as well as environmental benefits within a poultry farm.


Introduction Eggs represent an affordable source of protein. With respect to the increasing world’s population and a concomitant growing demand for protein, the egg producing industry strives for the common goal of an increased number of produced eggs via different strategies. Whereas, in developing countries, the number of laying flocks is on the rise, in industrial countries the main approach to succeed is to prolong the laying cycle of hens while improving laying persistency. Although a prolongation of the laying cycle will be mainly achieved by genetic selection of respective breeding lines, a bird’s nutrition significantly contributes to laying performance, especially during the late production period. A physiologically intact gastrointestinal tract ensures proper gut functions and therefore allows for the best utilization of nutrient resources. This, together with a healthy metabolism, is the prerequisite for keeping egg quality and eggshell quality on a high level throughout a bird’s life. Next to financial benefits, since the cost of one pullet will be reduced relative to the longer laying period, this will also have positive consequences for the environment. Bain and Dunn (2016) estimate, that the UK flock (including breeding hens) may be reduced


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by 2.5 million birds a year as long as one average hen is able to produce 25 or more eggs. Moreover, the authors highlight, that a prolongation of egg production for 10 weeks will save 1 g of nitrogen per dozen eggs, which will substantially reduce the nitrification impact of the egg producing industry.


Egg formation and industrial challenges A commercial layer can produce almost one egg daily, where the effective laying performance depends on the genetic predisposition, on some external factors (barn climate, season, ambient temperature or lighting regimes) and on nutritional supply. According to the farm and region, laying hens are housed in the production sites for about 80 to 85 weeks of age until they are replaced. Consequently, the longer this substitution of birds can be delayed, the higher is the economic output per hen. The economically limiting factor in the challenge of a prolonged laying cycle is keeping the laying persistency at a constant level and simultaneously stabilizing eggshell quality: the older the birds, the bigger the eggs – thus, the ratio eggshell to egg weight changes to a disadvantageous level as the relative thickness of the eggshell declines with increasing size of the egg, i.e. eggshell quality negatively correlates with bird’s age and the duration of the laying cycle. This instability of the eggshell results in a higher percentage of broken eggs which cannot enter the market as “table eggs” but are sold as “industry eggs” and this consequently leads to economic losses. Thus, with respect to farm profitability, the goal should be to obtain a high level of grade-A-egg portion in daily production. The stability of the eggshell is not only related to the extent of


calcification but moreover, the elasticity reflects the risk of getting damaged. The liver is the site of biosynthesis of the proteins responsible for the degree of elasticity. The older the laying hen is the longer several stressors act on the (liver) tissue causing damage and the higher the risk of infections. Thus, with increasing age, hens produce eggs with shells getting poorer in their elasticity, which additionally increases the risk of getting cracked in the further processing procedure on the farm. A healthy and well-functioning liver is a fundamental requirement for high level eggshell quality.


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