Prediction of Digestibility and Energy Value of Silage by in vitro Rumen Fluid and Enzymatic Methods

1 Thrakia University, BG-6000 Stara Zagora, Bulgaria
2 Research Institute of Mountain Stockbreeding and Agriculture, BG-5600 Troyan, Bulgaria


IANTCHEVA, N., N. TODOROV, D. PAVLOV and Ts. MIHOVSKY, 2003. Prediction of digestibility and energy value of silage by in vitro rumen fluid and enzymatic methods. Bulg. J. Agric. Sci., 9: 69–76

Relationships between in vivo organic matter digestibility (DOM,%) or metabolizable energy (ME MJ/kg OM) and different laboratory measurements have been calculated on 17 alfalfa silages and 20 corn silage. Laboratory measurements included Weende constituents, DM, fermentable products, and in vitro pepsin-cellulase digestibility of organic matter (CDOM,%), gas-production (GP, ml/24 h) and a modification of the two stage in vitro rumen fluid method (first step with rumen fluid was conducted in 100 ml glass syringes, second step was treatment with neutral detergent). The results from the latter procedure were expressed as true digestible OM (TDOM,%).
With TDOM the best regression equations for prediction of digestibility of organic matter (DOM) in vivo and metabolizable energy of alfalfa silage were obtained.
DOM(%) = 105-2711*1/TDOM R = 0.88 SEE = 2.83
ME(MJ/kg DM) = 1.05 + 0.11 *TDOMD + 0.03*EE + 0.005*FP R = 0.88 SEE = 0.42
Neither equations with chemical constituents + GP nor chemical constituents + CDOM reached the prediction accuracy of TDOM as sole parameter for alfalfa silage. The digestibility and metabolizable energy of corn silage could be predicted with considerable accuracy by using only chemical constituents. In vitro procedures could not essentially improve the prediction accuracy.
DOM (%) = 14.6 – 0.09*Ash + 0.06*CP + 0.08*DM + ().26*FP + 0.09*EE (R = 0.87, SEE = 1.94)
ME (MJ/kg DM) = -2.7 – 0.03*Ash + 0.03*EE + 0.03ooTF + 0.01*DM + 0.01*CP+0.03*FP (R = 0.88, SEE 0.40)

Key words: alfalfa, corn silage, digestibility, prediction