In the tropical Asian countries, information on nutrients availability from various by-products of agro-food industries remains scarce and even less is known about their application in the feed evaluation systems. The objective of this study was to generate renewed data on in situ rumen dry matter (DM) degradability of by-products from oilseeds, cereal grains, and animal origin, commonly fed to animals in tropical Asian countries. The data were used to derive regression equations to understand the relationships between effective rumen degradability of DM (ED_DM) and the rumen degradation characteristics of the by-products. Sixty four samples of five oilseed by-products, seven cereal grain by-products and four animal by-products were used. From each feed, 4 samples (~1 kg each) were collected from dairy farms (n=1), local markets (n=1) and different agro-industries (n=2). The feeds were incubated in the rumen for 2, 4, 8, 12, 24 and 48 h, using nylon bag technique. There was a significant (P<0.01) variation in the rumen degradation kinetics and ED_DM within by-products of oilseeds, cereal grains and animal origin. Regression analysis showed strong relationships (R² values above 0.90) between the ED_DM (g/kg DM) calculated using three rumen passage rates (0.04, 0.06 and 0.08 h^-1) and the washout (W) and rumen undegradable (U) contents (g/kg DM) of oilseed and cereal grain by-products. The renewed database is more reliable because all the by-product feeds were evaluated under uniform experimental conditions and the variation among sources of these feeds were also covered.

Key words: By-products, Effective rumen degradability, Nylon bag technique, Rumen degradation kinetics