Effect of sugarcane bagasse processing with alkalin compounds at different times on chemical compositions, digestibility and rumen fermentation parameters in vitro

Introduction: Due to reduced rainfall and degradation of rangelands, some portion of ruminant feed is provided by agricultural by-products such as cereal straws and sugarcan bagasse (SB). A key strategy for achieving environmentally sustainable added value and providing animal feed is to convert agricultural by-products into animal feed (Madadi et al 2023). Sugarcane is one of the most important economic crops worldwide and is mostly used as a raw material in the sugar industry and it is produced in more than 100 countries around the world. Its biomass can be used as animal feed in many countries more than any other forage. The SB is one of the fiberous residues that remain after water extraction from the sugarcane stalk and can be used as a source of fodder for ruminants (Pipitpukdee et al 2020). However, it has been reported that these by-products have low protein (less than 3% on DM basis), high cellulose (more than 40% on DM basis), high hemicellulose (more than 35% on DM basis), high lignin (15% on DM basis), and low DM digestibility (20-30%; Ahmed et al., 2013; Costa et al., 2013). Some livestock producers use unprocessed SB in ruminant nutrition, which is not accompanied by desirable results on animal performance (Nogueira et al 2022; Kraiprom et al 2022). Various methods including physical, chemical, and biological processing are used to change the physical and chemical nature of SB to improve its digestibility (Balgees et al 2007; Rezaii et al 2022; Khawar et al 2023). Therfore, the aim of this experiment was to investigate dry matter (DM) and organic matter (OM) digestibility and in vitro ruminal feremrntation parameters of diets containing sugarcan bagasse (SB) treated with urea (U) calcium hydroxide (CaH) at different times. Materials and methods: For each processing method, 6 one-kilogram samples of sugarcane bagasse were considered. One liter of solution was added to each kilogram of sugarcane bagasse and mixed thoroughly. Also, 6 one-kilogram samples of bagasse were considered as controls (without processing), and each was mixed with one liter of water without urea or calcium hydroxide. All samples inside 2-layer nylons were well compressed and sealed. Then, 3 one-kilogram samples of sugarcane bagasse mixed with alkaline solution and 3 control samples were silaged for 30 days and the rest for 45 days at room temperature. After the end of the desired time, the samples were taken out of the nylon and exposed to air for 5 days and stored for chemical analysis after drying. Then, experimental diets were prepared using these processed sugarcane bagasse samples.The SB was treated with solution containing different content of urea (4 or 3%) and calcium hydroxide (1 or 2%) for two times (30 or 45 days). Then, experimental diets were formulated by using treated SB. Experimental diets were 1- diet containing untreated SB stored for 30 days (Control, C-30), 2- diet containing treated SB with 4% U and 1% CaH stored for 30 d (U4CaH1-30), 3- diet containing treated SB with 3% U and 2% CaH solution stored for 30 d (U3CaH2-30), 4- diet containing untreated SB stored for 45 d (C-45), 5- diet containing treated SB with 4% U and 1% CaH stored for 45 d (U4CaH2-30), and 6- diet containing treated SB with 3% U and 2% CaH solution stored for 45 d (U3CaH2-45). Ingredients and chemical composition of experimental diets are shown in Table 1 and 2, respectively. The SB treated with different methods at different times and experimental diets were dried in an oven at 60 ° C for 48 hours, ground through a 1-mm screen using a Wiley mill, and analysed for dry matter (DM), organic matter (OM), crude protein (CP) (AOAC 2007), neutral detergent fibre (NDF) and acid detergent fibre (ADF) (Van Soest et al 1991). For measurement of methane production, the final gas production (end of 24 hours) was recorded after 24 hours of incubation of the sample in ruminal fluid + phosphate buffer. Experiment conducted by gas production technique (Menke and Steingass 1988) based on completely randomized design as 2×3 factorial. Results and discussion: The effect of different processing methods at different times on chemical composition of SB is shown in Table 3. Results showed that the highest DM content was observed in C-45 (P<0.05). Whereas, SB treated with 3% U and 2% CaH and preserved for 35 or 45 d had lower DM content compared to others (P<0.05). The highest and the lowest OM content were observed in SB untreated and preserved for 30 d and SB treated with 3% U and 2% CaH and preserved for 45 d, respectively (P<0.05). Treatment of SB with U and CaH increased crude protein (CP) content compared untreated SB (P<0.05). The SB treated with U and CaH and preserved for 30 or 45 d had lower neutral detergent fiber (NDF) compared to untreated SB (P<0.05). The highest ash content was observed in SB treated with 3% U and 2% CaH and preserved for 45 d (P<0.05). Ruminal fermentation parameters of diets containing SB processed by different methods at different times is shown in Table 4. The lowest 24 h comulative gas production (CGP) and OM digestibility were observed in C-30 and C-45 diets (P<0.05). Methan production, patitioning factor, efficiency of microbial mass production and DM digestibility did not influence by experimental diets (P>0.05). Gas production parameters of diets containing SB processed by different methods at different times are shown in Table 5. The U3CaH2-45 diet had higher 96 h CGP and gas production potential than other diets (P<0.05). The U3CaH2-30 and U3CaH2-45 had the lowest lag time (P<0.05). Diets containing SB processed with 3% urea solution and 2% calcium hydroxide solution and stored for 30 and 45 days had the highest cumulative gas production (P<0.05). Conclusion: In general, treatment of SB with 3% U and 2% CaH solution improved OM digestibility and gas production and can be used as a method for improvement of nutritional value of SB for using in diets of ruminant animals.