Arman sheep was synthesized by crossing of four sheep breeds, including Baluchi, Ghezel, Chios and Suffolk. Objective: to estimate the (co)variance components and genetic parameters using the restricted maximum likelihood via twelve animal models for lamb survival and four animal models for ewe productivity traits. Methods: data and pedigree information were collected at Abbasabad Sheep Breeding Station, Khorasan Razavi province, north-east of Iran from 1999 to 2011. Studied traits were lamb survival rate (LSR), litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lambing (LMWL), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Moreover, multivariate analyses were performed to estimate covariance between the traits. Results: direct heritability estimates (h2a) for LSR was 0.081 and increased to 0.253 after correcting. Maternal genetic effects (h2m) and common litter effects (l2) accounted for 4 and 11.3% of phenotypic variance for LSR. The estimations of h2a were 0.131, 0.080, 0.111, 0.190, 0.118 and 0.150 for LSB, LSW, LMWL, LMWLW, TLWB and TLWW, respectively. The estimated fractions of variance - attributed to permanent environmental effects on ewe - (pe2) were 0.038, 0.050, 0.071, 0.060 and 0.050 for LSB, LSW, LMWL, TLWB and TLWW. Service sire effects (S2) were significant for LSW, LMWL and TLWB being 0.038, 0.030 and 0.049, respectively. Direct genetic correlations showed a vast range from 0.13 for LSB-LMWL to 0.91 for LMWL-TLWW. Conclusions: results indicated that genetic change not only depends on the heritability of traits, but also on the observed phenotypic variation; therefore, non-genetic factors improvement should be included in breeding programs.

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