A study was conducted to asses the effect of incorporation of organochlorine pesticide (lindane) in feeds on In vitro rumen fermentation and substarte degradation. To the air dried forage sample lindane solution (0.01 ppm) was added into syringes to maintain the different levels of lindane (50, 100, 150, 200, and 250 % of MRL) in T-1, T-2, T-3, T-4 and T-5, respectively. Estimation of TVFA by using Markham apparatus and Ammonia nitrogen was done by calorimetric method. The pH of the supernatant was estimated by digital pH meter. Total gas produced in 24 h (ml/200 mg), pH, TVFA (mmol/100 ml) and NH3-N (µg/ml) remained similar in T-1, T-2 and T-3 treatments. However, these parameters were significantly (P<0.05) reduced in T-5 treatments, and T-4 exhibited intermediate position between T-5 and lower levels. Similarly, higher concentration of OCPs in feeds significantly (P<0.05) reduced TDOMR (mg/200 mg) and TDOMR (%), however, microbial-biomass production (mg/200 mg) and efficiency of microbial-biomass production remained unaffected 1349501582.php