Evaluation of arhar (Cajanus cajan) straw based pelleted feeds and prediction of in vitro gas production

Different ratios of concentrate (C) and grinded Cajanus straw (R) were used to prepare pelleted feeds, namely, T₁ (C:R=80:20), T₂ (C:R=70:30), T₃ (C:R=60:40), T₄ (C:R=50:50), T₅ (C:R=40:60), ₆ (C:R=30:70) and T₇ (C:R=100:00). The CP, EE, NFE and OM per cent in the substrates gradually decreased as Cajanus straw level increased in the pellets, whereas crude fiber and total ash levels showed the reverse trend. Based on the data of in vitro gas production (4-48h) polynomial regression equations were developed. Total gas production (ml) up to 48 h of incubation was significantly (P<0.01) higher in T₇ (187.81±0.59) than other treatments while lowest gas production was recorded in T₆ (124.86±0.68). The trend of methane production at 24 h and 48 h showed that methane percentage gradually enhanced in the in vitro bottles as Cajanus straw level increased in the pellets, but the differences were nonsignificant among treatment groups. In vitro dry matter degradability (IVDMD%) was highest (P<0.01) in T₇ (61.11±0.77) and lowest in T₆ (39.60±0.57). Nitrogen degradability (%) followed the similar trend of IVDMD. Addition of Cajanus straw increased pH in some treatments. TVFA (mmol/dl incubation medium) concentration was significantly (P<0.01) higher in T₁, T₂, T₃ and T₇ than other treatments. NH₃-N (mg/dl incubation medium) was also highest (P<0.01) in T₇ and lowest in T₆. Acetate and acetate: propionate ratio remained unchanged due to increase of straw, whereas, propionate level reduced significantly (P<0.05). Results showed that in vitro gas production, IVDMD and fermentation products decreased due to increase of Cajanus straw in the feed pellets.