Forty ewes (3-6 years of age, average weight 41.2 kg)were randomly chosen from the flock of the sheep experiment station of Tripoli University. Ewes were divided into two groups, control group (C) received untreated barley straw and treatment group (T) received barley straw treated with 10% urea solution applied as 40% (V/W). Barley straw was sprayed with molasses when fed to animals. Both groups received commercial concentrate according to physiological state. Experiment started by introducing the rams in June. Average concentrations of progesterone did not significantly differ and were 2.96 ng/mL and 2.38 ng/mL during 9 weeks for T and C groups, respectively. In T group, 53.3% of ewes were fertilized during the early period (two weeks after the introduction of the rams) and maintained levels of 3.5 ng/mL of progesterone. However, no ewes of C group were fertilized in this period. Conception rate, prolificacy and viability were 83.3%, 1.07 lamb/ewe, 93.75% and 78.94%, 1.13 lamb/ewe, 88.23% for T and C groups, respectively. These differences were not significant. Progesterone concentrations were below of 0.07 ng/mL during 9 weeks post-partum in both groups. Cereal straws can be treated with urea without adverse effects on reproductive performance. Manuscript profile