Aims: Study was undertaken to measure chemical composition and degradation kinetics of dry matter and neutral detergent fiber in the rumen for eleven different date pits that where cultivated in different parts of Iran. Study design: Ruminal degradation kinetics of the pit samples were determined using 3 Holstein steers (450-500kg body weight), fitted with permanent rumen fistulas. Data were fitted using an exponential equation of P=W+D (1−e−kd×(t-T)), where P is the potential of degradability, W is the quickly degradable fraction, D is the slowly degradable fraction; kd is the fractional degradation rate, t is the incubation time (h) and T is the lag time (h). Place and Duration of Study: The study took place at the Ruminant Nutrition Research Center of Agriculture Faculty of Ferdowsi University of Mashhad which placed at Mashhad urban zone. This study lasted 3 months. Methodology: Chemical composition, in situ DM and in situ NDF degradation kinetics in rumen of eleven different date pits (Barahi, Kabkab, Kharak, Khasi, Mazafati, mordabsang, Piarom, Rabbi, Estamaran, Shahani and Zahedi) were evaluated. Results: CP ranged from 5.00 to 6.90% DM and Mazafati pit had highest NDF content (78.23% DM) and Mordasang had highest ADF content (59.73% of DM) while Estamaran had lowest NDF and ADF content (68.90 and 50.50% of DM respectively). Mordabsang had the lowest W-fractionDM (0.104h) and Estamaran had the highest D-fractionDM (0.485). In contrast, Estamaran, Khasi, Mazafati and Zahedi had the highest (0.300, 0.301, 0.304 and 0.301 respectively) W-fractionDM and Piarom had lowest (0.323) D-fractionDM. The kdDM varied from 0.021/h (Mordasang) to 0.119/h (Estamaran). Piarom had the lowest WfractionNDF (0.011) and Estamaran had the highest W-fractionNDF (0.046). In contrast, Mazafati had the highest (0.603) and Piarom had lowest (0.394)) D-fractionNDF. Among the samples kdNDF varied from 0.021/h (Kharak) to 0.038/h (Estamaran). Conclusion: In conclusion our results show that pits of these date varieties can be used as fiber source for ruminants and their relatively high EE content may be useful as an energy source.

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