The experiment was performed in the Goat and Sheep farm, Department of Animal Science, Bangladesh Agricultural University, Mymensingh during the period from 21th May to 25th August 2018. The laboratory analysis was conducted in the Animal Science and Animal Nutrition laboratory of the Department of Animal Science and Animal Nutrition, respectively, Bangladesh Agricultural University, Mymensingh, Bangladesh.
Preparation of experimental materials
Fresh cow dung and wet rice straw were collected from Sheep and Goat farm, Bangladesh Agricultural University (BAU), Mymensingh. During collection, enough care was taken to avoid extra silica or other foreign substances. Molasses and air-tight plastic containers (30 L size) were purchased from the local market. After purchasing, the plastic containers were washed, cleaned, and dried properly. Plastic containers were labeled for different treatments.
Preparation of samples for chemical analysis
The wet rice straw was chopped into small pieces manually. Cow dung and chopped wet straw were subjected to determining the dry matter (DM) content of fresh samples. At the same time, another portion of fresh samples of both cow dung and wet rice straw were dried in the sun and then ground to pass through a 40 mm mesh sieve. After grinding, the samples were subjected to chemical analysis for organic matter (OM), crude protein (CP), crude fiber (CF), ether extract (EE), and total ash (TA) following the procedure of AOAC (2004). The following treatments were used in this experiment: T0 = 10% cow dung + 5% molasses + 85% wet rice straw T1 = 20% cow dung + 5% molasses + 75% wet rice straw T2 = 30% cow dung + 5% molasses + 65% wet rice straw T3 = 40% cow dung + 5% molasses + 55% wet rice straw The amounts of all of the above ingredients were measured on a DM basis.
Preparation of ensilage
Rice straw was collected just after harvesting. After collecting, wet rice straws were chopped about 3-4 cm long by chopper. Then ensilage was prepared by mixing chopped straw with fresh cow dung and molasses according to the above treatment. For proper mixing, cow dung and molasses were mixed first and then finally mixed with straw. When straw was properly mixed with cow dung and molasses, these were placed into air-tight plastic containers which were previously marked according to the treatment. Finally, plastic containers were kept in a room for 90 days for successful ensiling.
Organoleptic test and proximate analysis of ensilage
Ensilage samples were collected at 0, 30, 45, 60, and 90 days to observe how many days need to get a good ensilage. Finally, they were opened at 90 days. All the ensilage had a desirable pleasant aroma, yellowish in color, soft texture, and no mold growth observed on the top of any ensilage, indicating optimum fermentation. Acceptability of ensilages by cattle was also tested to test the palatability. Ensilage samples were taken and mixed thoroughly, to check DM in an air-dry oven at 105°C and pH by pH meter. To determine the nutritive value of the ensilage, respective dry samples were subjected to proximate analysis for crude protein (CP), crude fiber (CF), ether extract (EE), and Ash, following the methods of AOAC (2004) at Animal Science laboratory, Bangladesh Agricultural University, Mymensingh.
Determination of in vitro organic matter digestibility and metabolizable energy of ensilage
In vitro, organic matter digestibility (OMD) and metabolizable energy (ME) content of ensilage were done following the method described by Menke et al., (1979). Digestibility of organic matter (%) and metabolizable energy (MJ/kg DM) content were calculated according to the following equations by Menke and Steingass (1988). IVDOM = 16.49+0.9024 GP+0.0492CP+0.0387TA ME = 2.20+0.1357GP+0.0057CP+0.0002859EE2 Where, IVOMD = In vitro organic matter digestibility (%), ME = Metabolizable energy (MJ/kg DM), GP = Gas production expressed in ml per 200 mg DM, CP = Crude protein (g/kg DM), TA = Total ash (g/kg DM), EE = Ether extract (g/Kg DM).
Statistical analysis
A 4 ×5 factorial design with three replicates was used in the experiment. Data were statistically analyzed using SAS Statistical Discovery Software, NC, USA, and differences among the treatment means were determined by Duncan's Multiple Range Test (DMRT)