Ca salt of soybean oil (PSO) and that of mustard oil plus mahua oil (PMOMO) (50:50) were prepared using double decomposition method, and further tested for their fatty acid composition and degree of saponification. Furthermore, the different levels of protected fat of PSO and PMOMO were evaluated in wheat straw based total mixed ration (TMR) in vitro. Results indicated that capric, lauric, myristic, palmitic, steric, oleic, linoleic, leinolenic acids were traces, traces, traces, 10.00, 2.00, 25.00, 58.50, 5.0% in PSO while the corresponding values in PMOMO were 1.08, 0.28, 0.45, 16.9, 12.95, 44.38, 17.46 and 6.50%, respectively. The degree of saponification of both protected fat supplements was more than 80%. Six treatment combinations were tested I.e., blank without feed and fat supplement (T1); control diet with out fat supplement (T2); control diet plus bypass fat supplement (PSO) so that diet contain 5% fat (T3); control diet plus bypass fat supplement (PSO) so that diet contain 7.5% fat (T4); two more diets viz. T5 and T6 were formulated using bypass fat supplement from PMOMO containing 5 and 7.5% fat respectively. TMR was prepared using 50% concentrate mixture and 50% wheat straw. Result indicated that TVFA, $NH_3-N$,TCA-N, total-N and total gas production were increased in treatment diets at 7.5% level of supplementation, however, fermentation pattern remain similar at 5.0% level of supplementation with respect to control diet. Nevertheless, IVDMD and IVOMD values remained unchanged, rather non-significant at both fat levels and with the both fat sources. On the basis of results it was concluded that Ca-salt of Soybean oil or Mustard plus Mahua oil did not show any negative effect either on digestibility or on microbial protein synthesis in rumen, hence the dietary fat upto 7.5% level in total mixed ration based on wheat straw, could be safely used without any adverse effect on rumen fermentation.