title: Use of weaning management group as a random effect for a more robust estimation of genetic parameters for post-weaning traits in Nellore cattle.
abstract: Data from 69,525 animals were used to compare two types of analyses, one of them having the weaning management group (WEMANG) included as an effect in the contemporary group (F_WEMANG) and the other considering the weaning management group as a random effect, not related to the mathematical model (R_WEMANG) for post-weaning traits. The components of (co)variance were estimated for pre-weaning traits (birth weight and weaning weight) and for post-weaning traits [scrotal circumference (SC), weight gain from weaning to 18 months of age (WG) and muscle score (MUSC)] in Nellore cattle, based on a complete animal model. Heritability of SC, WG and MUSC for the F_WEMANG model was equal to 0.46 ± 0.02, 0.38 ± 0.03 and 0.26 ± 0.01, and for the R_WEMANG model it was 0.45 ± 0.02, 0.31 ± 0.03 and 0.25 ± 0.01, respectively. Genetic correlations between all the studied traits varied between 0.07 ± 0.01 and 0.77 ± 0.03 in F_WEMANG and between 0.02 ± 0.01 and 0.76 ± 0.04 in R_WEMANG. The R_ WEMANG model allowed a decrease in the number of contemporary groups as well as an increase in the number of observations per group without significant alterations in heritability coefficients, for the post-weaning traits. Consequently, the analysis became more robust and avoided having contemporary groups with low variability.
authors.affiliation: Grupo de Melhoramento Animal, Departamento de Zootecnia, Universidade Estadual de Ponta Grossa, Ponta Grossa, PR, Brasil vbpedrosa@uepg.br.
authors.forename: V B
authors.initials: VB
authors.lastname: Pedrosa
authors.affiliation: Grupo de Melhoramento Animal e Biotecnologia, Departamento de Ciências Básicas, Universidade de São Paulo, Pirassununga, SP, Brasil.
authors.forename: J P
authors.initials: JP
authors.lastname: Eler
authors.affiliation: Grupo de Melhoramento Animal e Biotecnologia, Departamento de Ciências Básicas, Universidade de São Paulo, Pirassununga, SP, Brasil.
authors.forename: J B S
authors.initials: JB
authors.lastname: Ferraz
authors.affiliation: Friedrich Loeffler Institute, Institute of Farm Animal Genetics, Department of Animal Breeding and Genetic Resources, Neustadt, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Groeneveld
mesh_terms: D000465:Algorithms; D000818:Animals; D001835:Body Weight / Q000235:genetics*; D001947:Breeding / Q000379:methods; D002417:Cattle / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D005260:Female; D008297:Male; D008957:Models, Genetic; D024510:Muscle Development / Q000235:genetics; D009132:Muscles / Q000033:anatomy & histology; D009929:Organ Size / Q000235:genetics; D019655:Quantitative Trait, Heritable; D012611:Scrotum / Q000033:anatomy & histology / Q000254:growth & development; D012641:Selection, Genetic; D014886:Weaning; D015430:Weight Gain / Q000235:genetics*