Investigation in early growth traits, litter size, and lamb survival in two Iranian fat-tailed sheep breeds.

In the present study, 1,635 lambing records of Ghezel (n=766) and Mehraban (n=869) breeds were used to evaluate the early growth traits, litter size, and lamb survival in sheep reared in Fars Province, southern Iran, during a 5-year-long period. The least squares means (± SE) of lamb birth weight for Ghezel were 5.27 (± 0.22), 5.02 (± 0.22), and 3.98 (± 0.23) kg for single males, single females, and twin lambs, respectively; whereas, the corresponding values for Mehraban were 4.39 (± 0.18), 4.18 (± 0.18), and 3.50 (± 0.19) kg. The least squares means of pre-weaning lamb growth (gram per day) for Ghezel were 239 (± 15), 218 (± 15), and 181 (± 16) for single males, single females, and twin lambs, respectively, and the corresponding values for Mehraban were 204 (± 12), 187 (± 12), and 156 (± 13). Lambs from 2 year old ewes or younger were on average lighter at birth and at weaning and had a lower average daily gain than those from older ewes (P<0.05). The percentage of twin births increased from 1.1 and 1.3 % for ewes aged ≤ 2 years to 19 and 12 % for those aged ≥ 6 years old in Ghezel and Mehraban, respectively (P<0.05). The mean pre-weaning lamb mortality was 7.1 and 4.1 % for Ghezel and Mehraban, respectively.