In vitro digestibility of forages supplemented with cellulose (filter paper) and branched-chain fatty acids or amino acids

Abstract

In vitro studies were conducted to determine dry matter (DM) digestibility of filter paper (FP), alfalfa hay (AA), corn silage (CS) and barley silage (BS) containing (as percent of DM) 0, 20 and 40% of FP and 0, 2 and 4% of either isoleucine (ILE) for CS, BS and FP, or its metabolite 2-methyl butyric acid (2MB) for AA. Digestibility of acid detergent fibre (ADF) of AA, CS and FP and of combinations of these forages with FP was determined. Digestibility of DM was determined after incubation with rumen fluid only or employing the two-stage Tilley and Terry technique. ADF digestibility was calculated after determining ADF in the original material and the residue after incubation for DM digestibility. Inclusion of FP increased (P < 0.05) digestibility of DM and ADF from 57.3 and 42.0 to 73.9 and 76.9% for AA and from 71.7 and 64.8 to 79.3 and 81.7% for CS, respectively. DM digestibility of BS increased (P < 0.05) from 65.7 to 74.6%. Addition of ILE to FP resulted in a quadratic (P < 0.05) increase in DM and ADF digestibility from 43.7 to 55.4 to 52.0% and from 47.4 to 55.1 and to 60.4%, respectively. Microbial protein produced after incubation with rumen fluid of all the forages and forage-FP combinations was determined using cytosine as a marker. Cytosine was determined in the incubated material and in the centrifugate. Increases in microbial protein production after addition of cellulose were noted for AA only. Key words: In vitro digestibility, forages, filter paper, isoleucine, 2-methyl butyric acid, cytosine, microbial protein