PREDICTION OF THE TOTAL TRACT DIGESTIBILITY OF ENERGY IN FEEDSTUFFS AND PIG DIETS BY IN-VITRO ANALYSES

An in vitro method consisting of a three-step enzymatic incubation for the prediction of total tract energy digestibility is described. The effects of all relevant parameters in the incubation conditions on the in vitro digestibility were investigated carefully in order to obtain a method with a general validity for all common feedstuffs used in pi g diets. A close linear relationship between the in vitro enzyme diges tibility of organic matter (EDOM) and in vivo total tract digestibilit y of energy (dE) was demonstrated for 90 samples of 31 different feeds tuffs: dE, % = -14.0(+/- 2.1) + 1.106(+/- 0.026) x EDOM, % (n = 90, r( 2) = 0.94, RSD = 3.4, CV = 4.4). Five samples of meat and bone meal an d raw potato starch were overestimated or underestimated, respectively , by the in vitro method. These two feedstuffs were therefore not incl uded in the equation. On the other hand, the equation was also valid f or experimental pig diets which were formulated with a considerable va riation in feedstuff composition and also including diets with these t wo feedstuffs. A close relationship between determined dE and predicte d dE for these feed mixtures by the use of the above equation was foun d (n = 34, r(2) = 0.87, RSD = 2.3, CV = 2.9). Thus, the described in v itro approach for energy evaluation appears to have a significant pote ntial for practical purposes. (C) 1997 Elsevier Science B.V.