Avian

Investigating the Genetic Background of Northern Fowl Mite Infestation on Cage-Free Laying Hens.

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Abstract

Northern fowl mite (NFM; Ornithonyssus sylviarum) infestation in cage-free laying hens presents ongoing economic and welfare challenges within North American egg production systems. While the effects of NFM on health, productivity, and welfare have been reported, limited information exists regarding the genetic background of individual hens' response to infestation. Controlled challenge trials enable the collection of standardized phenotypes for breeding to improve host response to NFM infestation in laying hen populations. Therefore, the main objectives of this study were to quantify phenotypic variability and estimate genetic parameters for various indicators of NFM infestation and host response traits in cage-free laying hens following an artificial NFM challenge. We assessed welfare- and immune-related variables to identify novel traits capturing variability in individual hens' responses to infestation and parasitic load. Traits were evaluated prior to and during infestation at 26, 30, and 40 weeks of age (WOA), including mite scores: 0 (no mites) to 7 ( >10,000), skin inflammation (0: no inflammation, 1: active, 2: recovering), inflammation area (in cm²), skin lesions (0: no lesions, 1: ≤2 cm, 2: >2 cm diameter wounds), and other welfare traits (e.g., feather score, beak score, keel bone damage) scored as 0 (not affected) or 1 (slightly affected) or 2 (affected). Records were collected on 1,030 White Plymouth Rock laying hens in two repetitions (400 in rep 1; 600 in rep 2; 30 "amplifier hens"), genotyped using the Axiom 54K SNP panel. GIBBSF90+ software was used to fit an animal model incorporating genomic information to estimate (co)variance components and genetic parameters for all traits. The model included the effects of contemporary group (room, pen, and repetition; n = 28), age (in days; fitted as a linear covariate), observer (n = 20), and a random effect of animal. Heritability estimates for mite scores, skin inflammation, inflammation area, and skin lesions ranged from 0.04±0.03 (40 WOA) to 0.10±0.04 (26 WOA); 0.04±0.02 (40 WOA) to 0.07±0.04 (30 WOA); 0.08±0.07 (40 WOA) to 0.11±0.05 (30 WOA); and 0.04±0.03 (40 WOA) to 0.05±0.03 (26 WOA). We observed substantial variability in the direction and magnitude of genetic correlations among trait pairs, including 0.86±0.01 between mite infestation at 26 WOA and skin inflammation at 30 WOA and 0.77±0.01 between mite infestation at 30 WOA and inflammation area at 40 WOA. In contrast, negative genetic correlations were observed between skin lesions at 26 WOA and mite count at 30 WOA (-0.52 ± 0.02). Overall, these results demonstrate that traits related to hen response to NFM infestation are measurable and heritable, highlighting the potential for improvement through genomic selection. These approaches have the potential to improve hen welfare and productivity while reducing the need for chemical interventions, supporting the long-term sustainability goals of the poultry industry.

Keywords: 2026

How to Cite:

Brito, L., Erasmus, M., Murillo, A., Oliveria, H., Sculley, E., Sutherland, H. & Wolc, A., (2026) “Investigating the Genetic Background of Northern Fowl Mite Infestation on Cage-Free Laying Hens.”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2279129. doi: https://doi.org/10.31274/wcgalp.23433

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