title: Genetic variation of the weaning weight of beef cattle as a function of accumulated heat stress.
abstract: The objective of this study was to identify the genetic variation in the weaning weight (WW) of beef cattle as a function of heat stress. The WWs were recorded at approximately 205 days of age in three Brazilian beef cattle populations: Nelore (93,616), Brangus (18,906) and Tropical Composite (62,679). In view of the cumulative nature of WW, the effect of heat stress was considered as the accumulation of temperature and humidity index units (ACTHI) from the animal's birth to weaning. A reaction norm model was used to estimate the (co)variance components of WW across the ACTHI scale. The accumulation of THI units from birth to weaning negatively affected the WW. The definition of accumulated THI units as an environmental descriptor permitted to identify important genetic variation in the WW as a function of heat stress. As evidence of genotype by environment interaction, substantial heterogeneity was observed in the (co)variance components for WW across the environmental gradient. In this respect, the best animals in less stressful environments are not necessarily the best animals in more stressful environments. Furthermore, the response to selection for WW is expected to be lower in more stressful environments.
authors.affiliation: Grupo de Melhoramento Animal de Mato Grosso (GMAT), Instituto de Ciências Agrárias e Tecnológicas, Universidade Federal de Mato Grosso, Campus Universitário de Rondonópolis, Rondonópolis, MT, Brazil.
authors.forename: M L
authors.initials: ML
authors.lastname: Santana
authors.affiliation: Grupo de Melhoramento Animal de Mato Grosso (GMAT), Instituto de Ciências Agrárias e Tecnológicas, Universidade Federal de Mato Grosso, Campus Universitário de Rondonópolis, Rondonópolis, MT, Brazil.
authors.forename: A B
authors.initials: AB
authors.lastname: Bignardi
authors.affiliation: Grupo de Melhoramento Animal e Biotecnologia (GMAB), Departamento de Medicina Veterinária, Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, SP, Brazil.
authors.forename: J P
authors.identifier: http://orcid.org/0000-0003-2939-4798
authors.initials: JP
authors.lastname: Eler
authors.affiliation: Grupo de Melhoramento Animal e Biotecnologia (GMAB), Departamento de Medicina Veterinária, Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, SP, Brazil.
authors.forename: J B S
authors.initials: JB
authors.lastname: Ferraz
mesh_terms: D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D005260:Female; D014644:Genetic Variation; D006358:Hot Temperature; D014886:Weaning; D014887:Weather
keywords: Genetic parameters; genotype by environment interaction; growth; reaction norm; temperature and humidity index