The Determination of Digestibility and Metabolizable Energy Levels of Some Forages Commonly Used in Ruminant Nutrition by in Vitro Methods

Abstract

This study was carried out to determine the dry matter (DM) and organic matter (OM) digestibilities, and metabolizable energy levels of some forages commonly used in ruminant nutrition by 2 different in vitro methods: the enzyme technique and the 2- stage method (rumen fluid + HCl-pepcine). Seven different samples of alfalfa hays, sainfoin hay and grass hay, and 4 different samples of wheat straws, lentil straw, corn silage and sorghum silage were used in the experiment. DM digestibilities were 51.53% for alfalfa hay, 47.79% for sainfoin hay, 41.02% for grass hay, 30.15% for wheat straw, 47.81% for lentil straw, 63.74% for corn silage and 53.25% for sorghum silage by the enzyme technique (P < 0.05). OM digestibilities and metabolizable energy levels were 57.93% and 9.11 MJ/kg DM for alfalfa hays, 52.68% and 8.28 MJ/kg DM for sainfoin hay, 46.37% and 7.31 MJ/kg DM for grass hay, 33.73% and 5.25 MJ/kg DM for wheat straw, 53.49% and 8.19 MJ/kg DM for lentil straw, 67.92% and 10.74 MJ/kg DM for corn silage, and 56.75% and 8.88 MJ/kg DM for sorghum silage by enzyme technique (P < 0.05). DM and OM digestibilities and metabolizable energy levels were 56.32%, 61.36% and 9.28 MJ/kg DM, respectively, for alfalfa hays, 50.21%, 56.21% and 9.07 MJ/kg DM, respectively, for sainfoin hay, 45.31%, 51.41% and 7.75 MJ/kg DM, respectively, for grass hay, 41.34%, 47.08% and 7.55 MJ/kg DM, respectively, for wheat straw, 49.67%, 56.56% and 9.16 MJ/kg DM, respectively, for lentil straw, 63.19%, 70.02% and 10.57 MJ/kg DM, respectively, for corn silage and 53.75%, 57.16% and 9.01 MJ/kg DM, respectively, for sorghum silage by the 2- stage method (P < 0.05). When the 2 techniques were compared, the estimations of DM and OM digestibilities and metabolizable energy levels by both techniques were similar (P > 0.05) in all forages, except for wheat straw. DM and OM digestibilities and metabolizable energy levels of wheat straw were lower with the enzyme technique compared to the 2- stage method (P < 0.05). In conclusion, the 2- stage method can be an alternative technique for determining forage digestibility and metabolic energy content to classical digestion trials.