Nest acceptance, clutch, and oviposition traits are promising selection criteria to improve egg production in cage-free system

Abstract

In cage-free systems, laying hens must lay their eggs in the nests. Selecting layers based on nesting behavior would be a good strategy for improving egg production in these breeding systems. However, little is known about the genetic determinism of nest-related traits. Laying rate in the nests (LRN), clutch number (CN), oviposition traits (OT), and nest acceptance for laying (NAL) of 1,430 Rhode Island Red (RIR) hens and 1,008 White Leghorn (WL) hens were recorded in floor pens provided with individual electronic nests. Heritability and genetic and phenotypic correlations of all traits were estimated over two recording periods–the peak (24–43 weeks of age) and the middle (44–64 weeks of age) of production–by applying the restricted maximum likelihood method to an animal model. The mean oviposition time (MOT) ranged from 2 h 5 min to 3 h and from 3 h 35 min to 3 h 44 min after turning on the lights for RIR and WL hens, respectively. The mean oviposition interval ranged from 24 h 3 min to 24 h 16 min. All heritability and correlation estimates were similar for RIR and WL. Low to moderate heritability coefficients were estimated for LRN (0.04–0.25) and moderate to high heritability coefficients for CN and OT (0.27–0.68). CN and OT were negatively genetically correlated with LRN (-0.92 to -0.39) except during peak production for RIR (-0.30 to +0.43). NAL was weakly to moderately heritable (0.13–0.26). Genetic correlations between NAL and other traits were low to moderate (-0.41 to +0.44). In conclusion, CN and OT are promising selection criteria to improve egg production in cage-free systems. NAL can be also used to reduce the number of eggs laid off-nest in these breeding systems. However, variability in MOT must be maintained to limit competition for the nests.

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

“…Data were collected daily for 40 weeks, when the hens were 24–64 weeks of age, except for the 2018–2019 batch of RIR, for which data collection was terminated at 58 weeks of age due to an infection (Table 1 ). The time of entry for nest visits with oviposition was used to calculate the clutch number (CN) and mean oviposition time (MOT) because it was strongly correlated with, and more reliable than, oviposition time [ 18 ], since eggs sometimes remained stuck in a nest until the hen left the nest, or even later (4.3% and 11.2% of eggs for RIR and WL, respectively). To compare the phenotypes to those reported in the literature, MOT was also calculated using oviposition time, when it was accurately measured (Table 2 ).…”

“…Conversely, a time difference less than 3 h for RIR and 3 h and 15 min for WL or in the other direction (i.e., an increase of the oviposition time) were attributed to hens laying floor eggs. Illustrations and more details are in a previous article and its appendix [ 18 ]. However, when a hen did not lay in a nest for more than four days, it was difficult to determine her activity (laying floor eggs or pausing).…”

“…Only hens that survived for at least half of the period were analyzed (Table 1). Egg production was defined as the laying rate in the nests (LRN): LRN, CN, MOT, and nest acceptance for laying (NAL) were calculated as described by [18]. In short, LRN phenotypes were kept for hens with LRN ≥ 50%, since low LRN can be caused by a variety of factors (e.g., preference for laying floor eggs, molting, repeated pauses) that make interpreting LRN more difficult.…”

“…Currently, no technology exists to easily identify which hens lay floor eggs in large groups. To select hens against laying of floor eggs and to optimize nest use, some studies have suggested selecting for nesting behavior traits and using radio-frequency identification with electronic nests to record these traits at the individual level and in large groups [16][17][18][19].…”

116. Laying hens tweet: they also lead and follow – implications for genetic selection against gregarious nesting

“…For a given 30-days period, LRN was the egg number laid in the nests divided by 30 and then multiplied by 100. The mean oviposition time (MOT) and the logarithm of the variance of oviposition time (LVOT) were calculated to characterize the laying rhythm, using a procedure described in Bécot et al (2021b). To consider the pre-laying behaviour referring to the nest choice for laying, the mean distance between nests of laying (MDN) was calculated.…”