Purpose Improving the nutritional value of rice straw by microbial inoculants and some physical treatments for animal feeding during dry seasons. Methods Different microbial inoculants and some physical treatments were used to improve the nutritional value of rice straw. Rice straw was divided into moist straw, soaked straw for 24 h without pasteurization and soaked for 24 h and pasteurized at 100 °C/1 h, and all of them were inoculated with different microbial inoculants. Results Moistened rice straw inoculated with Azotobacter chroococcum and Saccharomyces cerevisiae recorded the highest significant reduction in organic matter percent, 74.21%. The highest significant reductions in crude fiber, neutral detergent fiber, and acid detergent fiber percent were recorded in moistened rice straw inoculated with Azospirillum brasilense and Saccharomyces cerevisiae which gave 27.54, 55.39 and 42.47%, respectively. The highest significant increase in crude protein percent, 13.71%, was recorded in rice straw soaked for 24 h and inoculated with Azospirillum brasilense and Bacillus megaterium. The combined interaction between microbial treatments and physical pretreatments of rice straw gave a significant decrease in organic matter, crude fiber, neutral detergent fiber and acid detergent fiber %, as well as a significant increase in crude protein % compared to control. Addition of nitrogen fixers to rice straw improved its nitrogen contents. Conclusions This study showed the possibility of improving the nutritional value of rice straw using microbial inoculants and some physical treatments to produce safe and cheap animal feeds.

Sophisticated capital intensive waste-recycling technologies are unviable in small rural abattoirs in India due to low volume of wastes (principally blood and rumen digesta) generated and lack of infrastructural facilities. We report recycling of slaughterhouse wastes as an organic fertilizer, ‘bovine-blood-rumen-digesta-mixture’ (BBRDM). Bovine blood and rumen digesta were mixed in 3:1 ratio in a metallic container, boiled and stirred continuously till the mixture was largely free of water. The mass was sun-dried for 3 days to obtain the final product. BBRDM was applied for field cultivation of tomato (Lycopersicon esculentum L., local variety ‘Patharkuchi’) in West Bengal state (India) during 2012–13 and 2013–14. We compared tomato yields obtained with BBRDM (N:P2O5:K2O 30.36:1:5.75) and conventional inorganic fertilizers [diammonium phosphate (DAP), N:P2O5:K2O 18:46:0 + potash, N:P2O5:K2O 0:0:44]. BBRDM was applied at a higher rate compared with DAP + potash to meet the farmers’ desire for enhanced yields. 75 kg ha−1 was applied at the 2nd week while 150 kg ha−1 was applied at the 8th week after transplantation. Yields (total fruit weight) obtained from BBRDM-treated plants were higher in comparison with DAP + potash-fertilized plants by 46–48% as the former supplied 2.5 times more nitrogen (N) than the latter. The partial factor productivity of DAP + potash was 73–76% higher than BBRDM. Conversely, as BBRDM was produced through local entrepreneurship from slaughterhouse wastes, the cost of this organic product would be expected to be much lower than the commercial inorganic fertilizer. Furthermore, application of BBRDM negates the environmental cost of treating slaughterhouse effluent. Considering the same cost of applying 225 kg fertilizer ha−1, higher yield with BBRDM should result in greater potential revenue for the farmer compared with yields with DAP + potash. The C/N ratio of BBRDM is 4.8, having relatively high N content. Accordingly, rapid release of plant-available N was observed in BBRDM-fertilized soils. The temporal increase in soil NH4+may be attributed to lack of soil N immobilization. Local farmers are willing to accept the new fertilizer as a substitute for currently used chemical fertilizers.

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Environmental and health safety of recycled slaughterhouse wastes-derived fertilizer and the produce obtained through its application is not well understood. Waste bovine blood and rumen digesta were mixed, cooked and sun-dried to obtain bovine-blood-and-rumen-digesta-mixture (BBRDM, NPK 30.36:1:5.75). 1.26 ± 0.18 log CFU mL −1 fecal coliforms were recovered in BBRDM. E. coli O157:H7, Mycobacteria, Clostridium sp., Salmonella sp., Bacillus sp. and Brucella sp. were absent. No re-growth of pathogens was observed after 60 days storage in sealed bags and in the open. However, prions and viruses were not evaluated. Heavy metals (Pb, Cr, Cd, Cu, Zn, As, Ni, Mn) concentrations in BBRDM were within internationally permissible limits. BBRDM was applied for field cultivation of tomato during 2012-2013 and 2013-2014. Lycopene and nitrate contents of BBRDM-grown tomatoes were higher than Diammonium OPEN ACCESSAgriculture 2015, 5 827 phosphate (DAP) + potash-grown tomatoes because BBRDM supplied 2.5 times more the amount of nitrogen than DAP (NPK 18:46:0) + potash (NPK 0:0:44). Heavy metals and nitrate/nitrite concentrations in tomatoes were within internationally acceptable limits. BBRDM-grown tomatoes showed no mutagenic activity in the Ames test. Sub-acute toxicity tests on Wistar rats fed with BBRDM-grown tomatoes did not show adverse clinical picture. Thus, no immediate environmental or health risks associated with BBRDM and the tomatoes produced were identified.