This paper presents an experiment of the preparation of ensilage with wet rice straw (WRS) treated with biogas slurry (BGS) and ensiled with molasses to increase the nutritional and preservation quality of straw in monsoon season of Bangladesh in the Department of Animal Science, Bangladesh Agricultural University (BAU), Mymensingh. Chopped wet straw was preserved in plastic containers under airtight condition at room temperature based on the treatments as T 0 (100% WRS only), T 1 (0% BGS), T 2 (5% BGS), T 3 (10% BGS) and T 4 (15% BGS) with 5% molasses as DM basis in each treatment except T 0 to investigate physical quality, chemical composition, in vitro organic matter digestibility (IVOMD) and metabolizable energy (ME) content at 0, 30, 45, 60 and 90 days. The highest CP content was found to be 7.70% in T 4 and highest DM and EE content were found to be 31.42 and 4.86% in T 0, respectively. The lowest CP and DM content were found to be 4.02 and 21.94% in T 0, respectively and lowest EE content was found to be 3.13% in T 4 . The CP and DM were increased (P<0.05) and EE were decreased (P<0.05) with the increasing of ensiling time from 0 to 90 days. The highest OMD and ME content were found to be 48.46% and 6.98 MJ/Kg DM in T 4 and the lowest OMD and ME content were found to be 34.31 and 4.84% in T 0, respectively. The pH value was also decreased (P<0.05) with the increasing of BGS and ensiling time. Considering all the physical and chemical properties, among all the treatments, T 2 and T 3 are acceptable for preparing ensilage. Ensilage of WRS with biogas slurry will not only reduce waste disposal and pollution problem, but also provide inexpensive feed components for ruminants.

Bio-slurry, a byproduct of biogas plant is not using properly and most of the cases causing environmental and social hazard by discharging it in public places though it rich in nutrients especially protein (16-20% CP) and produced through beneficiary anaerobic microorganisms. On the other hand, Straw is highly fibrous residue having low protein (CP <3%) content which mostly indigestible. The poor digestibility of straw is further caused by the presence of high amount of inhibitory mineral element called silica. The combination of low intake, low degradability, low nitrogen content and an imbalanced mineral composition means that rice straw alone may not even meet the animal's maintenance needs. Therefore, the animals are suffering from nutrients deficiencies resulting in poor health and productivity of these animals reared on straw based ration. Under this situation, it is essential to find out the ways and means to increase the supply and quality of feed to livestock to fulfill their deficiencies. So, the way to improve the crude protein, metabolizable energy and preservation quality, wet rice straw can be ensiled with biogas slurry. The principles of ensiling process of straw are maintenance of anaerobic conditions throughout the ensiling and rapid decline in pH value by lactic acid bacteria. Ensiling of wet rice straw along with biogas slurry may produce a good quality ensilage for feeding cattle having desire palatability, nutrient content and digestibility and also reduce the environmental pollution.