Introduction: The profitability of livestock production depends to a great extent on the cost of feeding animals, which is often the principal production cost. The animal feed production industry consumes large quantities of imported raw materials, including cereals and oilseed cake. This high dependence on imports, fluctuating prices and a lack of standardization concerning the composition of the raw materials, are constraints for the industry, which is keen to find a solution (Shamma et al 2003). In the last years the valorisation of agricultural co-products is receiving more attention, co-products contain valuable substances; they are good sources of dietary fiber. Many agricultural co-products are rich in dietary fibers. Ruminants could extract nutritional components through symbiotic relationships with microorganisms, including bacteria and protozoa, present in their digestive apparatus. The main benefit of these microorganisms is their ability to convert different vegetable materials rich in fiber, and with no use in human food, into products of high biological value such as milk and meat (Kasapidou et al 2015). Most parts of Iran have arid and semi-arid climate, and there is feed shortage for livestock during the year. Use of agro-industrial co-products in animal diet is an alternative way to overcome feed shortage (Shamma et al 2003). Agro-industrial co-products, can be effectively consumed by ruminant species. One of the agro-industrial co-products are medicinal plant residue. These distilled leaves and residues do not have a specific commercial use and could be included in livestock diet. This experiment was aimed to study the in vitro rumen fermentation kinetic of rose flower distillation residues and fumaria distillation residues and experimental diets containing different levels of rose flower distillation residues or fumaria distillation residues. Material and Methods: Fresh rose flower distillation residues and fumaria distillation residues were collected from an agro industry processing factory (Gareh Ban, Harsin, Kermanshah province). Chemical compositions (dry matter, neutral detergent fiber, acid detergent fiber, crude protein and ash), in vitro gas production parameters, total protozoa population and N-ammonia concentration of rose flower distillation residues and fumaria distillation residues were measured. Each pulp separately included at three levels (10, 20 and 30 % of DM) in a basal diet. Experimental diets were:1- Basal diet, 2- basal diet containing 10% of rose flower distillation residues, 3- basal diet containing 20% of rose flower distillation residues, 4- basal diet containing 30% of rose flower distillation residues, 5- basal diet containing 10% of fumaria distillation residues, 6- basal diet containing 20% of fumaria distillation residues and 7- basal diet containing 30% of fumaria distillation residues. Basal diet formulated for ewes and contained 12.5 % CP and 2.20 Mcal metabolisable energy (ME) /Kg of diet. In vitro gas production parameters, total protozoa population and N-ammonia concentration of diets were measured and metabolizable energy (ME), short chain fatty acids (SCFA) and organic matter digestibility (OMD) were estimated. For in-vitro gas production, rumen fluid was taken from two rumen fistulated Kordish rams. For measuring gas production, 200 mg of experimental diets were incubated with 40 ml of buffered-rumen fluid for 120 hours. The cumulative produced gas was recorded at different times of incubation and gas production parameters were fitted with Blummel et al. equation (2003). Organic matter digestibility (OMD) was estimated after 24 hours of incubation (Menke and Steingass 1988). N-ammonia concentration was measured based on the method of Broderickand and Kang. (1980). Rumen protozoa were identified according to the method of Dehority et al. (2003). After 24 h incubation, 5 ml of buffered rumen fluid was pipetted into a screw-capped test tube containing 5 ml of formalin. Thereafter, two drops of brilliant green dye (2 g brilliant green and 2 ml glacial acetic diluted to 100 ml with distilled water) were added to the test tube, mixed thoroughly, and allowed to stand overnight at room temperature. Total and differential counts of protozoa were made with five replications. In-vitro rumen concentration of volatile fatty acids (VFA) was measured by gas chromatography (Ottenstein and Bartley 1971). All invitro gas production trials were carried out in three runs. Protozoa population, ammonia-N, SCFA, ME and OMD data were analyzed based on a completely randomized design and gas production data was analyzed based on a complete randomized block design using Proc GLM of SAS software. The differences among treatments were evaluated using Tukey adjustment when the overall F-test was P ≤ 0.05. In addition, independent comparisons were done for diets containing rose flower distillation residues vs. diets containing fumaria distillation residues. Results and Discussions: The results showed that rose flower distillation residues contains 130.6, 425.5 and 308.5 g/kg of CP, NDF and ADF respectively and fumaria distillation residues contains 143.4, 473.7 and 347.4 g/kg of CP, NDF and ADF respectively. Gas production, ammonia-N and total protozoa population were not different between rose flower distillation residues and fumaria distillation residues, but rose flower distillation residues had greater gas production rate than fumaria distillation residues (0.057 vs 0.047 %/h, P<0.01). Diet inclusion of rose flower distillation residues or fumaria distillation residues increased gas production in compare to basal diet (P<0.01). Diet containing 30 % of rose flower distillation residues had the highest gas production (90.05 ml/200 mg DM), gas production rate (0.034 %/h), OMD (58.38%), SCFA (1.07 mmol/200 mg DM) and ME (9.47 MJ/kg DM) (P<0.01). Basal diet had the highest ammonia-N concentration (16.77 mg/dl, P<0.01) among experimental diets. Conclusions: Considering the obtained data regarding the chemical compositions and gas production parameters, it can be concluded that rose flower distillation residues and fumaria distillation residues could be used as a part of forage portion in ruminant nutrition. [ABSTRACT FROM AUTHOR]