Processing of Roughages | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Processing of Roughages

• Roughages are a crucial component of the diet for farm animals, consisting of green fodder (both leguminous and non-leguminous), grasses, and various crop residues like wheat and rice straws, barley, jowar, maize stalks, and bajra.
• During periods of green fodder scarcity, alternative options such as sugarcane tops, bagasse, and sunflower heads are utilized to supplement the animals' diet.
• Long-stemmed green fodders are typically chopped before feeding, while succulent fodders are either wilted or combined with dry crop residues to prevent bloat risk.

Physical Methods of Chopping/Grinding

Chopping/Grinding

Definition: 

• Chopping or grinding involves cutting green fodders and crop residues into small pieces either manually or using power-operated machines.

Manual Method:

• Manual chopping involves the use of sharp tools like gandasa or a machine known as toka with blades operated by rotating a vertical wheel.
• Fodder is fed into the machine, which chops it into fine (0.5 cm) or coarse (1-2 cm) pieces.

Power-Operated Method:

• Power-operated toka machines require less manpower and are more efficient.
• Power consumption varies based on the material's characteristics like moisture content, thickness, fiber level, and strength.

Advantages of Chopping:

• Facilitates feeding and reduces wastage.
• Aids in mixing with other ingredients and prevents selective feeding.
• Increases bulk density for easier handling.
• Enhances digestion by exposing a larger surface area to microbial digestion.

Application:

• Chopped materials are commonly mixed with water-soaked feed ingredients or compounded feed to create a balanced animal diet.
• This mixture is often referred to as Saani.

Effect on Digestibility:

• Studies have shown that chopping oat hay can increase dry matter intake but may not significantly affect nutrient digestibility.
• Improved intake is mainly attributed to higher bulk density and faster digestion by rumen microbes.

Economics of Chopping

• Labor charges are set at Rs 4.0 per hour per head.
• Wastage of unchopped straw is 40% while that of chopped straw is 10% during feeding.

When considering the economics of chopping paddy straw, a key feed for animals in India, certain aspects come to light. Labor costs are fixed at Rs 4.0 per hour per head. Additionally, there is a notable difference in wastage between unchopped and chopped straws, with unchopped straw seeing a 40% wastage rate and chopped straw experiencing a lower 10% wastage during the feeding process.

Crop Residue Utilization Study Summary:

• Power chopping is the most cost-effective method for utilizing crop residue efficiently.
• Unchopped materials lead to more wastage, which can be recycled through animals to produce more dung for composting, a more effective method than composting straw-mixed dung.
• Chopped residue is typically mixed with dung to create cow dung cakes for fuel purposes.

Impact of Particle Size on Crop Residue Digestibility:

• Grinding crop residue reduces particle size but only moderately increases surface area due to the length-width relationship of fibers.
• Research has shown that feeding ground dried grass to cows results in faster intake compared to long dried grass, impacting rumination time significantly.
• Reducing particle size affects rumination and saliva secretion, with processed feed materials typically stimulating less saliva production.

Effects of Physical Form on Rumen Fermentation:

• Feeding oats hay in various forms (long, chopped, ground) along with a fixed concentrate mixture alters rumen fermentation and liquid digesta flow rate through the gastrointestinal tract.
• Rao and Thakur's study on oats hay reported changes in rumen fermentation based on the physical form of the hay.

Effects of Grinding Crop Residues:

• Grinding crop residues enhances voluntary consumption and reduces water intake due to decreased saliva secretion.
• Despite increased dry matter intake, the benefits of grinding are offset by faster digesta passage, resulting in less retention time.
• Chopping crop residues is recommended over grinding to avoid the need for additional power and costly equipment.

Utilization of Crop Residues:

• In regions where animals are primarily fed crop residues without concentrated mixtures, maintaining them in a long form allows selective consumption of nutritious leaves.
• This method leads to the wastage of less nutritious organic matter, which, when mixed with dung and urine, can be composted and recycled as manure.
• While this practice is beneficial in areas with abundant crop residues, it may not be suitable in regions already facing a scarcity of dry roughage.
• Recycling such material through animals increases dung availability for composting, biogas production, and manure utilization.

Soaking as a Processing Method for Crop Residues:

• Soaking is a cost-effective technique commonly used to enhance the taste of chopped crop residues, particularly wheat straw. This method is preferred for wheat straw due to its lack of pith, ensuring that the chopped material is thoroughly dried and rigid.
• The soaking process serves to soften the straw and eliminate dusty particles. It transforms hard straw nodes, typically unpalatable to animals, into a chewable form, making this portion consumable by animals.
• Wet straw becomes adhesive during soaking, encouraging animals to ingest both the straw and other palatable feed ingredients mixed with it. This results in improved voluntary intake and nutrient digestibility, as demonstrated by experiments on soaked wheat straw.
• Typically, straw is submerged in an adequate amount of water for 4-6 hours. Before feeding, the water is completely drained. This practice is uncomplicated and economical, requiring no significant expertise or financial investment.
• In certain regions, straw and other components are submerged directly in the feeding trough to conserve water and labor. Animals consume water and soaked feed together, enabling efficient nutrient utilization and saving labor and feed resources.

Other Methods of Processing Roughages:

• Apart from chopping and soaking, individual animal owners can consider other processing methods like ensiling and hay making. However, these techniques are not commonly adopted by Indian farmers due to the scarcity of green fodder, limited potential for enhancing the nutritional value of low-grade roughages, and the need for expertise, financial resources, and labor.

Steam Treatment Technology

Overview of Steam Treatment:

• Steam treatment is a process that involves subjecting crop residues to high-temperature steam under pressure, aimed at enhancing their nutritional value.

Working Principle:

• High-temperature steam breaks down chemical bonds in crop residues, leading to various degradations that ultimately improve the digestibility of the product.

Application in Sugar Mills:

• Steam treatment is particularly feasible in sugar mills where steam is readily available and can be used to process byproducts like bagasse.

Research Findings:

• A study by Rangnekar et al. (1992) investigated the impact of steam pressure treatment on sugarcane bagasse, paddy straw, and sorghum straw at different pressures and treatment times.
  (i) Effects on Digestibility: The treatment had a positive effect on the digestible dry matter of bagasse and sorghum straw, although some dry matter losses were observed for all crop residues.
  (ii) Pressure and Treatment Duration: Higher steam pressure and longer treatment periods resulted in more significant dry matter losses, emphasizing the importance of optimizing treatment conditions.

Chemical Methods

• Chemicals like alkalies (such as NaOH, NH3, urea, Ca(OH)₂), acids like sulfuric acid, and oxidizing agents (e.g., bleaching powder) have been extensively used to achieve certain objectives in various laboratories.
• Caustic soda (NaOH) treatment is highly effective in breaking ligno-cellulosic bonds, providing energy for rumen microorganisms. Ammonia (NH₃), despite being a weak alkali, can be more effective for straw enhancement when nitrogen sources are limited.
• The efficacy of ammonia in upgrading straws depends on factors like its concentration, temperature, treatment duration, moisture level, and initial material quality.
• Urea has been explored as a safer alternative to gaseous ammonia for ammoniating crop residues. Studies in India have indicated that 4% urea (of straw dry matter) with 40% moisture over 10 to 30 days under controlled conditions is highly effective.
• Long-term feeding trials comparing ammoniated and untreated wheat straw have shown improved cattle and buffalo performance, particularly highlighted at the International Workshop in NDRI, Karnal.
• However, feeding freshly harvested paddy straw ensiled with urea (4%) to buffalo calves as the primary nutrient source resulted in low crude protein digestibility. Various experiments have also raised doubts about the nitrogen value of ammoniated straw.
• When straw was supplemented with urea at a lower level (2% of straw dry matter) instead of being ammoniated, nitrogen utilization was found to be more efficient.