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ILVO - KU Leuven - Pluimveehouderij Press Release - Wednesday, October 25, 2017

From 360 to 500 eggs per hen?

Layers can keep laying eggs much longer with the right feed, management and choice of genetics. Split feeding, where older hens get the right combination of fine and coarse limestone at certain times of day, can combat a decline in eggshell quality. “The egg production per hen can be increased by up to 40%, but egg farmers must be able to transition to split feeding,” says researcher Anikó Molnár, who will soon defend her doctoral thesis on this subject. Another important result: white hens do better in a longer production cycle than brown hens.

KU Leuven  Antwerp

On 10 November 2017 Anikó Molnár will defend her doctoral thesis: “Extended Production Cycle in Laying Hens – The Role of Nutrition and Management” at KU Leuven.

Older layers: pros and cons

more eggs

Today’s layers are kept for 75-80 weeks and are expected to lay about 360 eggs. For reasons of sustainability and profitability, egg farmers and researchers are striving to find ways to keep layers for up to 100 weeks. Keeping layers longer means less costs for breeding and less frequent cleaning of the stall. But a longer laying cycle has disadvantages as well: declining egg production, declining egg and bone quality, and health and welfare problems for the hens. The biggest problem, however, is eggshell quality: older layers produce shells with more fragile shells. ILVO researcher Anikó Molnár thus studied how to increase eggshell quality during longer laying cycles. Her attention went mostly to adjusted feeding and management.

Stronger shells by presenting limestone at the right times of day

The solution for stronger shells seems simple: often, people think that by just adding more limestone to the feed of older layers, the shell problem will be solved. But how much limestone, how frequently, and in what form? By testing “split feeding”, an alternative strategy that provides a different feed composition in the morning and afternoon, it is possible to determine when and which type of limestone makes a difference in shell quality. Split feeding was tested in small experiments with hens older than 75 weeks at ILVO as well as in a practice-sized experiment at the Center for Poultry Research in Geel, Belgium. During those tests it was studied whether split feeding is possible for commercial egg production in enriched cages and volière systems.

In terms of the form and percentage of limestone to feed for an optimal egg quality, the results at ILVO differed clearly for brown and white layers. Brown layers of 72-83 weeks that received a split feeding with a morning feed without added limestone and an afternoon feed with added fine and coarse limestone (ratio 30:70) ate less and had 40-47% fewer broken eggs in comparison to the control group. But even though the eggs were stronger, the shells were not thicker. For white hens of 75-92 weeks of age, the same amount of limestone but presented as fine limestone in the morning and coarse limestone in the afternoon, presented more advantages for maintaining good eggshell quality. These results were confirmed at commercial scale in enriched cages. In the volière system, the administration of split feeding was very difficult because feed is given on different levels of the system. This probably explains why neither production nor eggshell quality improved in the volière system.

During the feed trials at the Experimental Center the older layers in both housing systems had various health and welfare problems. The negative effects of these problems have influenced the general performance of the hens and possibly also the results of our tests. This underscores the need to track not only eggshell quality but also health and welfare of the birds.

Keeping hens longer is possible but will require further optimization

These results imply that depending on the hybrid, the limestone administration can be adjusted based on form (fine or coarse), percentage and time of addition. But despite these efforts, the effect on shell quality may be limited. “The influence of limestone on eggshell quality is also related to factors such as gut health. Adding limestone has little effect if it cannot be taken up in the intestines,” says the researcher. This calls for further research.

When asked, “Is it possible and feasible to keep layers longer?” Ms. Molnár answers affirmatively: “Commercial layers already have the potential to live productively up to 100 weeks and to produce 500 eggs. From a Flemish field study done within in this doctoral study, the egg quality of older layers does appear to diminish, but at 80 weeks of age they still meet the requirements for table eggs. The reduction in egg quality only appears at the end of the cycle. In an extended laying period of 100 weeks, this can be dealt with via split feeding. But to successfully extend the laying cycle, we must look beyond shell quality and examine bone and gut health and feather picking as well.”


Greet Riebbels, ILVO communication:, +32 486 26 00 14
Evelyne Delezie, ILVO promotor,, +32 473 46 86 01
Anikó Molnár, doctoral student,