The aim of the present study was to evaluate the effects of pomegranate peel and soybean oil on performance, nutrient digestibility, ruminal microbial population and blood biochemical parameters in feedlot lambs. For this purpose, 48 male lambs with an average weight of 30 ± 0.40 kg were used in a 75-day rearing period. Treatments were 1) control diet (without additives), 2) diet containing 3% soybean oil, 3)diet containing 10% pomegranate peel, 4) diet containing 10% pomegranate peel and 3% soybean oil,5) diet containing 20% pomegranate peel and 6) diet containing 20% pomegranate peel and 3% soybean oil. The results showed that pomegranate peel and soybean oil alone were not effective on dry matter intake (DMI), however, their combination (20% pomegranate peel and 3% soybean oil) showed to have significant effects on DMI. Organic matter digestibility in lambs consumed 20% pomegranate peel was higher than those fed control diet. Soybean oil had supplementation resulted an increase (P<0.01) in ruminal protozoa population, compared to control group. However, pomegranate peel had no significant impact on protozoa number. The effect of pomegranate peel was significant on ruminococcus albus, ruminococcus flavefaciens and total microbial population (P<0.01). Furthermore, the population of ruminococcus flavefaciens was affected by adding 3% soybean oil (P<0.01). The combination of pomegranate peel and soybean oil significantly affected both ruminococcus albus and ruminococcus flavefaciens (P<0.01). Pomegranate peel, soybean oil and their combination had no impact on growth performance of lambs. Pomegranate peel and soybean oil in combination supplementation significantly decreased blood BUN, total triglyceride and TAC concentration (P<0.05), compared to control diet. Moreover, pomegranate peel alone decreased (P<0.05) BUN, ALT, ALP, TAC and HDL, compared to control diet.
