Survival analysis of genetic and non-genetic factors influencing ewe longevity and lamb survival of Ethiopian sheep breeds T. Getachew a,b , S. Gizaw c , M. Wurzinger a , A. Haile d , B. Rischkowsky d , A.M. Okeyo e , J. Sölkner a,n , G. Mészáros a a University of Natural Resources and Life Sciences, Department of Sustainable Agricultural Systems, Division of Livestock Sciences, Gregor Mendel Strasse 33, A-1180 Vienna, Austria b Debre Berhan Agricultural Research Center, P.O. Box 112, Debre Berhan, Ethiopia c International Livestock Research Institute, Addis Ababa, Ethiopia d International Center for Agricultural Research in the Dry Areas, Addis Ababa, Ethiopia e International Livestock Research Institute, Biotechnology Theme, Nairobi, Kenya article info Article history: Received 4 December 2014 Received in revised form 22 March 2015 Accepted 24 March 2015 Keywords: Awassi Menz Longevity Survival Risk ratio Weibull abstract Survival analysis applying proportional hazards models was used to investigate genetic and non-genetic factors affecting ewe longevity and lamb survival of sheep in Ethiopia. Data were obtained from an on-station closed nucleus breeding program of Menz sheep and an on-farm Awassi  Menz sheep crossbreeding project. A total of 695 ewes and 1890 lambs born from the nucleus population of Menz sheep were used for the analysis of ewe productive life and lamb survival to yearling age respectively. In addition, 5530 lamb records of purebred local and crossbreds with proportions of 25–50% Awassi, collected from three locations were used for the analysis of lamb survival from birth to weaning age. The effects of year, ewe parity and litter weight at weaning were significant (p o0.05) for ewe productive life. On-station lamb survival to yearling was affected by year and breeding value of yearling weight of the lamb, indicating that faster growing animals had substantially higher survival rates. Animal model heritability estimates for lamb mortality ranged from 0.02 to 0.10. While there was a strong genetic trend for growth rate, as evidenced by estimated breeding values for different birth years, estimated breeding values for lamb survival were variable across years with decreasing trend. These results indicate no antagonism between growth rate and survival under conditions prevailing in the nucleus system. Routine genetic evaluation for survival is suggested. Under farmer conditions, the effects of year, season, sex and location effects were significant (p o0.05) on lamb survival to weaning age whereas breed composition (local versus crossbred) of dam as well as of the lamb were not significant. This seems to indicate that crossbreeding of local animals with Awassi sheep does not have an adverse effect on the survival of lambs under farmer conditions typical for the Ethiopian highland regions included in this study. & 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/livsci Livestock Science http://dx.doi.org/10.1016/j.livsci.2015.03.021 1871-1413/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ43 69910442312. E-mail address: johann.soelkner@boku.ac.at (J. Sölkner). Livestock Science ] (]]]]) ]]]–]]] Please cite this article as: Getachew, T., et al., Survival analysis of genetic and non-genetic factors influencing ewe longevity and lamb survival of Ethiopian sheep breeds. Livestock Science (2015), http://dx.doi.org/10.1016/j. livsci.2015.03.021i