Digestibility, chemical compound and protein quality of amaranthus forage at two harvested cut

Introduction Amaranth, genus Amaranthus, belongs to the Amaranthaceae family and includes more than 60 species (28). Amaranth forage, is distinguished by high yield performance of up to 70 t/ha (30). Plant maturity was found to affect neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, CP and nitrate content of amaranth forage (27). Several studies (21, 27, 29) have shown that the nutritive value of amaranth as a ruminant feed is equal to, or better than, commonly used forages such as alfalfa. Its favorable chemical analysis (e.g., high crude protein (CP) and low lignin ranges from 80 to 285 and from 17 to 73 g/kg DM, respectively) and its high dry matter (DM) digestibility (590–790 g/kg DM) low nitrate and oxalic acid concentrations (below toxic levels) suggest that it has potential value as a ruminant feedstuff (21, 23, 27). Materials and Methods The forage was planted in spring at one field (10 ha) near Karaj city (Iran). The area is at an altitude of 1215 m above sea level, with a mean annual rainfall and temperature is 305.8 mm and 15C◦, respectively. In the early autumn, samples were harvested by hand from at least 10 locations within the field and pooled to five samples. The dry samples were analyzed for DM (method 930.15), ash (method 924.05) and CP (method 9 84.13) of AOAC (6). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) according to the method of Robertson and Van Soest (35) with NDF and ADF assayed sequentially without a heat stable amylase, and expressed inclusive of residual ash (25). Insoluble CP, soluble CP (SP), true protein (TP), AD insoluble CP (ADICP) and ND insoluble CP (NDICP) were determined according to Licitra method (15). Nitrate was determined by a colorimetric method (8), and oxalic acid was determined according to Abaza method (2). Ca and Mg were determined by atomic absorption, P was analyzed by spectrophotometer and K by flame emission spectrometer (6). DMD, OMD and DOMD were determined by a two stage technique for the in vitro digestion of forage crops (32). In a completely randomized experiment with factorial arrangement (2×2) the digestibility, chemical compound and protein quality of two varieties of amaranthus including: Kharkof (K), A. Spp.(S). which were planted as forage crops and harvested at two cuts, were studied. Data were subjected to analysis using the GLM procedure of SAS (26), using the statistical model: Yijk = µ + Vi + Dj + Vi Dj + eijk Results and Discussion Results of in vitro two st