In Vivo fermentable organic matter (FOM) reflects the energy production and the potential of rumen's microbial protein synthesis. However, the in vivo method with fistulated animals for FOM measurement compromises animal welfare and is laborious as well as expensive. Although the alternative in situ nylon bag technique has been widely used, it is also costly and requires rumen liquor. Therefore, the present study was performed to compare the in situ nylon bag technique with the in vitro neutral detergent cellulase (NDC) method or chemical composition to estimate in vivo FOM of roughages. For this purpose, we selected 12 roughages, including six each from forages and crop residues. Our results have shown the strong correlation equations between FOMin situ and FOMNDC of forages (n = 6; R2 = 0.79), crop residues (n = 6; R2 = 0.80), and roughages (n = 12; R2 = 0.84), respectively. Moreover, there were also strong correlations between the chemical composition of roughages and FOMin situ (n = 12; R2 = 0.84-0.93) or FOMNDC (n = 12; R2 = 0.79-0.89). In conclusion, the in vitro NDC method and chemical composition were alternatives to in situ nylon bag technique for predicting in vivo FOM of roughages in the current experiment.
Keywords: fermentable organic matter; in situ nylon bag technique; in vitro neutral detergent cellulase plus amylase method.