The objective of this study was to investigate the effect of rumen-protected L-arginine (ARG) on the udder of ewes and growth rate of newly born lambs. At 15±3 days postpartum, ten clinically healthy, 3-4 years ewes with body weight 49.11±4.03 Kg were divided randomly into 2 equal groups Group 1: served as control, without any treatment. Group 2: treated with Rumen protected L-Arginine 20 Mg/Kg body weight,for 30 days. The animals were examined with ultrasound, and blood samples were taken at the 10th, 20th and 30th days of ARG supplementations begin, and the lambs were weighted in the same times. The results of this study revealed that significant differences (P<0.05), between ARG treatment and control one, in some udder measurement's. The glucose concentration after 10, 20, and 30 days of treatment showed significant differences (P<0.01, and 0.05), where the ARG reatment had higher glucose concentration than control. Also,there were significant differences (P<0.05), between ARG treatment and control group, in the urea and AST concentrations. There was an increase in the lamb's body weight at 10th, 20th and 30th Day of ARG treatment. The ARG supplementation appeared to have significant
effects on postpartum udder measurements as well as the growth rate of the newly born lambs.