title: Robustness to chronic heat stress in laying hens: a meta-analysis.
abstract: Chronic heat is a major stress factor in laying hens and many studies on the effect of heat stress have been published. It remains difficult, however, to draw general conclusions about the effect of chronic heat stress on performance and its relationship with genetic and environmental factors, as these studies have been done under varying experimental conditions and using various experimental designs. A meta-analysis enabled us to make a quantitative review of the results from 131 published papers. The relative effects of four factors (genotype, age, group size, and amplitude of temperature variation) and their interactions with temperature were analyzed for 13 traits. After pre-correcting the data for a random study effect, the best model for each trait was selected in a stepwise procedure based on its residual sum of squares. Shell strength, daily feed intake, egg mass, and hen-day egg production were found to be more sensitive to heat stress than the other traits as they dropped by 9.0 to 22.6% between thermo-neutrality (15 to 20°C) and heat stress (30 to 35°C) while yolk and albumen proportions or Haugh units showed nearly no variation with temperature (<1.2% between thermo-neutrality and heat stress). Many interactions (17) were found between temperature and one or more factors in the 13 traits studied here, which reinforces the interest of using a meta-analysis to summarize data from the literature. This study highlighted that the impact of heat stress in laying hens depends on the genotype, age, and group size, some of which have rarely been investigated.
authors.affiliation: UR083 Recherches Avicoles, INRA, 37380 Nouzilly, France sandrine.grasteau@tours.inra.fr.
authors.forename: S
authors.initials: S
authors.lastname: Mignon-Grasteau
authors.affiliation: UR083 Recherches Avicoles, INRA, 37380 Nouzilly, France WUR Animal Breeding and Genomics Group, P.O. Box 338, 6700 AH, Wageningen, the Netherlands AgroParisTech UFR Génétique Elevage et Reproduction, 75231 Paris cedex 05, France.
authors.forename: U
authors.initials: U
authors.lastname: Moreri
authors.affiliation: UR083 Recherches Avicoles, INRA, 37380 Nouzilly, France.
authors.forename: A
authors.initials: A
authors.lastname: Narcy
authors.affiliation: UR083 Recherches Avicoles, INRA, 37380 Nouzilly, France.
authors.forename: X
authors.initials: X
authors.lastname: Rousseau
authors.affiliation: UR083 Recherches Avicoles, INRA, 37380 Nouzilly, France.
authors.forename: T B
authors.initials: TB
authors.lastname: Rodenburg
authors.affiliation: UMR1313 GABI, INRA, Domaine de Vilvert, 78352 Jouy-en-Josas cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Tixier-Boichard
authors.affiliation: UMR1313 GABI, INRA, Domaine de Vilvert, 78352 Jouy-en-Josas cedex, France.
authors.forename: T
authors.initials: T
authors.lastname: Zerjal
mesh_terms: D000367:Age Factors; D000818:Animals; D002645:Chickens / Q000235:genetics / Q000502:physiology*; D005260:Female; D005838:Genotype; D018882:Heat Stress Disorders; D006799:Housing, Animal; D012098:Reproduction; D013696:Temperature
keywords: egg production; egg quality; heat stress; layer; meta-analysis