m Aubi - Postgraduate student of animal science, Islamic Azad University of Khorasgan Branch.
s.n Tabatabaei - Assistant Professor of Animal Science, Islamic Azad University of Khorasgan Branch,and Agriculture and Natural Resource Research Center of Shahrekord.
f Zamani - Assistant Professor of Animal Science, Islamic Azad University of Khorasgan Branch,and Agriculture and Natural Resource Research Center of Shahrekord.

The data used for this study were collected in 9 nomadic flocks (4 flocks Bakhtiari and 5 flocks Ghashghaei) in Esfahan province. Data collected on 900 lambs born alive in the different flocks were included in the analyses. Average pre-weaning mortality rate was 19% and ranged from 17.5% for Bakhtiari flocks to 20.4% for Ghashghaei flocks. Mortality rate in male lambs was higher than that recorded for female lambs (P<0.05). When comparing the management systems followed from mating up until weaning in the different flocks with the corresponding pre-weaning mortality rates, it is obvious that there was discernible trend. Of the 171 lambs deaths recorded, the probable cause for 157(91.1%) deaths was known. The most important problems were health issues and disease, malnutrition, management and welfare. About 45.03% of pre-weaning mortalities was due health issues and disease. Birth weight and sex of the kid had a significant influence on pre-weaning mortality rate. Single-born kids had the lowest mortality rate, followed by twin-born and triplet-born lambs.

Lamb, Mortality , Bakhtiari, Ghashghaei, Nomadic