Genetic and non-genetic analysis of lamb survival in Sangsari sheep by gibbs sampling method
2019
Lima, Maziar Jafari | Rokouei, Mohammad | Dashab, Gholam Reza | Seyedalian, Ahmad Reza | Faraji-Arough, Hadi
The aim of this study was to investigate the genetic and non-genetic effects on survival traits of Sangsari sheep from birth to the last recording date. Data base with 35,470 sheep survival records was collected during 1988 to 2010 in 11 flocks by the Animal Breeding Center of Iran. The non-genetic effects were evaluated on hazard rate of sheep in different times with survival and cmprsk packages. Exponential distribution based on censored data was used to estimate the genetic parameters of the survival from birth to the last recording date. The linear animal models were fitted using Bayesian method via Gibbs sampling of the MCMCglmm package. The overall mortality rate for Sangsari lambs was 2.00 and 25.72% for birth to 100 and 500 day of age, respectively, and its value increased upto 90.54% till 3400 day of age. The results indicated that the year and month of birth, sex of lamb, birth weight, age of ewe, flock (P < 0.001), and type of birth (P < 0.01) had a significant effect on sheep survival. Estimated direct heritability for survival from birth to the last recording date by different linear models ranged 0.097 to 0.157. The contribution of maternal permanent environmental variance ratio was estimated higher than maternal heritability, thus this effect must be considered in the evaluation models for improving sheep survival. The present findings suggest that sheep survival improvement could be possible through management practice as well as genetic selection.
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