Nutritional evaluation of rice straw from different rice cultivars
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Rice straw is an abundant cheap feed resource that can be used in various feeding systems to reduce on feed costs. However, it is of poor nutritive value but measures such as breeding can improve its nutritional composition. This study was conducted to evaluate the nutritional value of straw from five newly developed rice cultivars (JA2019, JA2019-2, JA2019-4, JA2019-5 and JA2019-6) The cultivars were planted in five homogeneous plots. Plant height and tiller number at maturity were determined and after grain harvest, rice straw was harvested from randomly selected plants from each plot and a composite sample of straw was made for each plot/ rice cultivar. The straw was analysed in the laboratory for its chemical composition some from which other parameters were estimated as well. Rice cultivar JA2019 had the highest(P<0.05) height at 99.9 cm while cultivar JA2019-4 was the shortest (52.1cm). The tiller number produced by the different cultivars ranged from 12-21 with cultivar JA2019-4 producing a higher(P<0.05) number of tillers than the other cultivars. Considering chemical composition, straw from cultivars JA2019, JA2019-5 and JA2019-6 contained higher (P<0.05) crude protein (9.3, 9.3 and 8.7%, respectively) compared to straw from the other two cultivars. Significant variations (P<0.05) were observed in the NDF content of the straw which ranged from 66.9-71.0% with straw from JA2019-2 having the highest NDF while straw from cultivar JA2019-5 had the lowest. Straw from cultivar JA2019-2 contained significantly (P<0.05) higher (42.1%) levels of ADF than straw from the rest of the cultivars. The total ash content was highest(P<0.05) in straw from cultivar JA2019-5(15.4%) followed by the level (11.8%) from JA2019-6. For the DMI estimates as a percentage of body weight, straw from cultivar JA2019-5 showed significantly higher(P<0.05) DMI (1.80% BW) followed by straw from cultivars JA2019 and JA2019-6 at 1.77%BW and 1.76%BW respectively. It was also observed that the DMD of the straw differed significantly (P<0.05) ranging from 56.1% to 63.7%. A significantly higher(P<0.05) RFV (88.7%) was observed in straw from cultivar JA2019-5 than that from cultivars JA2019-6, JA2019, JA2019-4 and JA2019-2 at 86.6, 85.9, 78.0 and 73.5 respectively. This study showed that rice cultivars JA2019, JA2019-5 and JA2019-6 produced the best quality straw in terms of chemical composition and utilisability by livestock. Straw from these cultivars can improve rice straw based feeding systems by improving livestock productivity at lower feeding costs. However, the NDF content of the straw was high ranging from 66.9 to 68.2% which is still a nutritional problem. Pre-treatment of this rice straw can further improve on its nutritional quality. Measures such as ensiling, alkali treatment and treatment with microorganisms can help to reduce on the fibre content of this straw thereby enhancing its digestibility and intake.