title: (Co)variance components and genetic  parameters for growth traits in Arabi sheep using  different animal models.
abstract: The  objective of the present study was to estimate genetic parameters for body  weight at different ages in Arabi sheep using data collected from 1999 to 2009.  Investigated traits consisted of birth weight (N = 2776), weaning weight (N =  2002) and weight at six months of age (N = 1885). The data were analyzed using  restricted maximum likelihood analysis, by fitting univariate and multivariate  animal models. All three weight traits were significantly influenced by birth  year, sex and birth type. Age of dam only significantly affected birth weight.  Log-likelihood ratio tests were conducted to determine the most suitable model  for each growth trait in univariate analyses. Direct and total heritability  estimates for birth weight, weaning weight and weight at six months of age  (based on the best model) were 0.42 and 0.16 (model 4), 0.38 and 0.13 (model 4)  and 0.14 and 0.14 (model 1), respectively. Estimation of maternal heritability  for birth weight and weaning weight was 0.22 and 0.18, respectively. Genetic  and phenotypic correlations among these traits were positive. Phenotypic correlations  among traits were low to moderate. Genetic correlations among traits were  positive and higher than the corresponding phenotypic correlations. Weaning  weight had a strong and significant correlation with weight at six months of  age (0.99). We conclude that selection can be made in animals based on weaning  weight instead of the present practice of selection based on weight at six  months.
authors.affiliation: Department of Animal Science, School of Agriculture, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran. Borhansh@Iausdj.ac.ir
authors.forename: B
authors.initials: B
authors.lastname: Shokrollahi
authors.forename: H
authors.initials: H
authors.lastname: Baneh
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001724:Birth Weight / Q000235:genetics*; D001835:Body Weight / Q000235:genetics*; D005260:Female; D005838:Genotype; D008297:Male; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012756:Sheep / Q000235:genetics* / Q000254:growth & development; D014886:Weaning