title: Environmental and genetic  factors affecting the weaning-estrus interval in sows.
abstract: We examined  the effects of environmental and genetic factors on the weaning-to-estrus  interval (WEI) in sows. In order to perform the analyses of the environmental  factors, 8104 observations of the 1st to the 6th WEI were carried out, while  6548 observations of the 1st to the 3rd WEI were carried out for the analyses  of genetic factors. The environmental model included as fixed effects, herd,  genetic line, year and season of birth, as well as the covariates, age of sow  at farrowing, litter size at birth and lactation length. Genetic analysis was  performed by repeatability and multitrait models. The mean and coefficient of  variation for WEI were 7.02 days and 100.6%, respectively. The linear effect of  lactation length and the quadratic effect of the age of sow at farrowing  affected the WEI. Herd, year and season of farrowing were significant sources  of variation for WEI, and there was no influence of genetic line or of litter  size at birth. Heritability estimated by the repeatability model was 0.04,  while heritabilities obtained by the multitrait model were 0.07, 0.02 and 0.07  for the first three WEI, respectively. Estimates of genetic correlations among  the different WEI were of moderate to low magnitude. It was concluded that  environmental factors, such as year and season of farrowing, lactation length,  age of sow at farrowing and herd, should be considered in the model for best  estimation of genetic parameters for this trait. Although with only a small  possible genetic gain, selection can be made based on the first WEI.
authors.affiliation: Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, MG, Brasil. carla.leite@ufv.br
authors.forename: C D S
authors.initials: CD
authors.lastname: Leite
authors.forename: J F
authors.initials: JF
authors.lastname: Lui
authors.forename: L G
authors.initials: LG
authors.lastname: Albuquerque
authors.forename: D N M
authors.initials: DN
authors.lastname: Alves
mesh_terms: D000818:Animals; D030762:Estrous Cycle / Q000502:physiology*; D005260:Female; D059647:Gene-Environment Interaction; D007774:Lactation / Q000502:physiology; D008954:Models, Biological; D040641:Quantitative Trait Loci / Q000502:physiology*; D013552:Swine / Q000502:physiology*; D014886:Weaning