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Why select laying hens in cage-free conditions?

In European Union, 50% of commercial laying hens were reared in cage-free (soil, free-range, and organic) systems in 2018, 30% back in 2009, and 8% back in 1996 (ITAVI, 2019). These systems provide for laying hens living conditions that consider their sensitivities better. Today, laying hens are mainly selected in individual cages, to enable individual recording performance. The rearing conditions of the nucleus are now very different from those of commercial hens, especially in cage-free systems. Indeed, in these systems, hens are raised in a large group and must lay in nests to ensure eggs collection. The majority of eggs laid off-nest cannot be marketed because they are broken by hens or soiled with droppings. Collecting these eggs is also laborious work for the farmer as it must be collected by hand. Selecting hens on nesting behavior is an opportunity to reduce this off-nest laying.

How to record the hen’s nesting behavior?

Figure 1: Principle of electronic nest

Some electronic nests were developed by the breeding company Novogen to record nesting behavior under cage-free conditions (figure 1). Little is known about the genetic background of nesting behavior traits, such as time of entry or time spent in the nest. However, these traits could be the origin of competition of hens for nests, potentially leading off-nest laying. Electronic nests also make it possible to measure egg quality traits (with egg-hen awarding) as well as reproductive rhythm traits, such as the number of clutches (figure 2), already known in individual cages to improve the number of eggs laid by selection. (Chen and Tixier-Boichard, 2003; Wolc et al., 2019).

Figure 2: Laying patterns in nests of three hens (A: short clutches, B: long clutches, and C: clutch without pause) recorded with electronic nests for 140, between 24 to 43 weeks of age. Blue points represent eggs laid, and blue lines connect eggs when there is no day without data that separate the eggs, i.e. a pause day (green triangles) or an egg laid off-nest (red arrows).

Aims of the thesis

This thesis aims to acquire knowledge to optimize the breeding program of laying hens reared in cage-free systems. Our objectives are:

• Study the genetic background of nesting behavior traits and reproductive rhythm traits as well as their genetic correlation with the laying rate in the nest and egg quality traits.
• Study the genotype-by-environment interactions (cage and cage-free) for traits measured in the two types of breeding systems.
• Identify the relevant traits to be included in the breeding program of hens adapted to cage-free systems.

Lorry Bécot is working on this subject since February 2020 for 3 years. He is supervised by Pascale Le Roy and Nicolas Bédère in the genetic and genomics team.

Contacts

Lorry Bécot : lorry.becot[at]inrae.fr (Ph.D. student);
Pascale Le Roy : pascale.le-roy[at]inrae.fr (supervisor);
Nicolas Bédère : nicolas.bedere[at]inrae.fr (co-supervisor).

Bibliography

• Chen C., et Tixier-Boichard M., 2003. Correlated responses to long-term selection for clutch length in dwarf brown-egg layers carrying or not carrying the naked neck gene. Poult. Sci. 82:709–720. DOI.
• ITAVI, 2019. Situation du marché des œufs et ovoproduits - Edition novembre 2019. 11p.
• Wolc A., Jankowski T., Arango J., Settar P., Fulton J.E., O’Sullivan N.P., et Dekkers J.C.M., 2019. Investigating the genetic determination of clutch traits in laying hens. Poult. Sci. 98:39–45. DOI.