Nest preference and laying duration traits to select against floor eggs in laying hens

Abstract

Background: Floor eggs, which are defined as eggs that hens lay off-nest, are a major issue in cage-free layer poultry systems. They create additional work for farmers because they must be collected by hand. They are also usually soiled or broken, which results in economic losses. Nonetheless, knowledge about the genetics of nesting behavior is limited. The aim of this study was to estimate genetic parameters for traits related to nest preference for laying and to time spent in the nests used for laying (laying duration).

Methods: Two pure lines of laying hens were studied: 927 Rhode Island Red and 980 White Leghorn. Electronic nests were used to record the nesting behavior of these hens in floor pens from 24 to 64 weeks of age. Nest preference was studied based on the mean distance between nests used for laying and the percentage of nests used for laying. Laying duration was studied based on mean laying duration, mean duration in the nest before laying, and mean duration in the nest after laying. Genetic parameters were estimated for each line using a restricted maximum-likelihood method applied to a pedigree-based multi-trait animal model.

Results: Estimates of genetic parameters were similar for the two lines. Estimates of heritability ranged from 0.18 to 0.37 for nest preference traits and from 0.54 to 0.70 for laying duration traits. Estimates of genetic correlations of these traits with clutch number or mean oviposition time were favorable. Positive genetic correlations were estimated between nest preference and laying rate in the nests or nest acceptance for laying (+ 0.06 to + 0.37).

Conclusions: These results show that genetics influences traits related to nest preference and laying duration. Selecting hens that have no preference for particular nests and spend little time laying in the nests could help optimize nest use, reduce their occupation rate, and thus decrease the incidence of floor eggs in cage-free systems. Genetic correlations of these traits with other traits of interest related to hen welfare and egg quality have yet to be estimated.

Fig. 1

Least-square means of the laying duration traits for each line and 28-day period. MLD mean laying duration, MDB mean duration in the nest before laying, MDA mean duration in the nest after laying. Different letters indicate a significant difference between periods

Fig. 2

Heritability (h²) and genetic correlations (r_g) of laying duration traits by line and 28-day period. MLD mean laying duration, MDB mean duration in the nest before laying, MDA mean duration in the nest after laying. Standard errors for h² and r_g ranged from 0.05 to 0.12

Fig. 3

Genetic (${\sigma }_a^2$) and residual (${\sigma }_e^2$) variances of laying duration traits by line and 28-day period. MLD mean laying duration, MDB mean duration in the nest before laying, MDA mean duration in the nest after laying. Different letters indicate a significant difference between periods