Effect of dietary manipulation on methane production in crossbred cattle

Male crossbred cattle (9; 280kg body weight, 1.5- 2.0 yr old) fitted with rumen fistula were divided into three equal groups and fed concentrate mixture with wheat straw in 25: 75 (T₁), 50: 50(T₂) and 75.25 (T₃) ratio. Digestibility of DM, OM, CP and EE increased significantly (63.3 to 79.9, 65.2 to 81.9, 60.3 to 72.3 and 48.2 to 62.2) with the level of concentrate mixture from 25% to 50%, however, variation between T₂ and T₃ was not significant. Production rate of TVFA also increased significantly (P<0.05) from 17.2 ± 0.79 (T₁) to 24.8 ± 0.44 (T₃) mole/d, with significant (P<0.01) decrease in acetate (%) from 62.7 ±0.53 to 50.6 ± 0.72 and increase in propionate (%) from 25.9 ± 0.45 to 35.8± 0.28. Rumen liquor (RL) of these animals was used to estimate in vitro methane production from substrates containing concentrate mixture and wheat straw in different ratios ranging from 0 to 100. Net gas produced ranged from 99.3 to 131.8 1/kg DM and showed an increasing trend with the increase in the level of concentrate, while methane (%) decreased from 41.1 ± 2.90 (0% straw) to 17.5 ± 2.02 (100% straw). Based on these values, methane production by growing, dry and lactating animals for various body weight and dietary concentrate level was calculated. It can be inferred from these results that in vitro fermentation corresponds to in vivo system and its results can be used to predict in vivo methane production by taking into account the DMI of the animals.