2.4 Chemical analyses
Chemical compositions (concentrate and silage) were presented in g/kg of DM after oven-drying at 65°C for 24 h and milling through a 1 mm (AOAC, 1998; ID 934.01). Ash content was measured by combustion at 550°C for 16 h (AOAC, 1998; ID 942.05) to determine the organic matter (OM). Nitrogen concentration was determined by the Kjeldahl method (AOAC, 1998; ID 988.05). After, the CP was calculated by N content multiplied by factor 6.25. Ether extract content was determined by method ID 920.39 (AOAC, 1998). Neutral detergent fibre (NDF) content was measured according recommendations of Mertens (2002) using alpha-amylase and expressed inclusive of residual ash. The acid detergent fibre was measured using AOAC method (1998; ID 973.18) and expressed inclusive of residual ash. Total carbohydrates (TC) was estimated following the procedure of Sniffen et al. (1992). Non fibrous carbohydrate (NCF) was determined as the difference between TC and NDF. Metabolisable energy of feedstuffs was estimated according to the NRC (2000) recommendations.