Global breeding programs

Effect of field test size on response to selection for egg production in layer chickens

---

Abstract

Evaluation of crossbred sibs in a target, challenging environment brings valuable information for selection of pure line candidates housed in biosecure and environmentally controlled farms due to higher similarity to commercial production but is associated with significant costs. Therefore, optimization of the size of a field test program is important for breeding companies. The objective of this study was to compare alternative layer breeding programs with field test data on 400, 1000, or 2000 crossbred progeny per reciprocal cross. Additional traits included in the selection index, with equal weights, were single-bird cage egg production recorded on 1000 female selection candidates per line and multi-bird cage production recorded on 250 purebred full-sib groups per line. The scenarios were compared in terms of genetic gain and inbreeding rate using stochastic simulation in MoBPS. Only egg production was simulated, which is the most important trait in layers, but the results can also be interpreted in terms of subindices of traits collected in different environments. Simulated heritabilities were 0.1 for field test production, 0.15 for multi-bird cage production, and 0.2 for single-bird cage production, with positive genetic correlations assumed between the different data sources. All selection candidates were genotyped. GEBVs were calculated using single-trait, single step GBLUP, using phenotypes on 3 previous generations but without data available on the candidates or their sibs at the point of selection. Field test birds were simulated as F1 of two lines from a common origin, separated by 40 generations of random mating. Each generation was assumed to have a fixed population structure with 20 selected sires and 120 dams. Responses over ten generations of selection were evaluated using GEBVs of pure line selection candidates, with ten replicates per scenario. Increasing field test size from 400 to 2000 resulted in a significant 16% increase in genetic gain for field test production (p=0.034). Multi- and single-bird cage production also showed numerical increases in genetic gain with increasing field test size, but not statistically significant (p >0.05) due to high variability between replicates. Inbreeding rate was similar for all 3 scenarios, with an average of 2% per generation. The results likely depend on assumptions used for the simulation, including genetic parameters and index weights, and, therefore, sensitivity analysis is needed to determine which assumptions are most critical for the success of a breeding program that aims to increase commercial production of layer chickens.

Keywords: 2026

How to Cite:

Wolc, A., van der Beek, S., Settar, P. & Dekkers, J., (2026) “Effect of field test size on response to selection for egg production in layer chickens”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286991. doi: https://doi.org/10.31274/wcgalp.24189

Rights: 1