Production of Silage from Sugarcane Tops: A Challenge
Nutan Chauhan and Neelam Kumari
ICAR-National Dairy Research Institute, Karnal, Haryana
India is facing an extreme animal feed shortage, which is a major factor behind the recent rise in costs of milk production. According to the report, there is a deficit of 23.4 % in availability of dry fodder, 11.24 % in the of green fodder. As for green fodder, shortage was steepest in Jharkhand (67%), it is followed by Uttarakhand (55%) and Odisha 44.8%. Feed deficit is a critical problem for livestock production. The root causes are limited grazing land and underdeveloped forage production. Traditionally, green fodder is natural feedstuff to fulfil the requirement of livestock. Agriculture is the primary source of income for about 58% of India’s population. So, little available land for cultivation of fodder which nourish to livestock. As a result animals mainly depend on agriculture by products (<44%).This is less palatable and low in nutritional quality .These are the main issue on better utilizing crop residues and improving diet quality for ruminants in India to increase production. Due to urbanization and increase the human population dairy products demand will increase day by day.
About 282 lakh tonnes per annum sugarcane is produced in India. Green tops are used as cattle feed during the harvesting period (Nov. to April).Without any suitable utilisation major part are left as such or burnt in filed. However, seasonal harvesting of high accumulated sugarcane tops waste increase rapidly environmental pollution and greenhouse gas emissions. In recent years, utilisation of agriculture by products as an alternative feed ingredient has extensively promoted to reduce requirement of traditional feed material. Therefore, strategies needed to foster and impede these pollutants could contribute toward a cleaner, greener and sustainable livestock production. Preservation practice has considerable potential, preserved sugarcane tops silage can be provided as green fodder for livestock during lean period.
Silage making process dependant on many factors, such as the natural microbial population, sugar content of the forage and harvesting conditions. As a result, silage quality can be changeable and the only way to successfully control the fermentation process is to use an additive. Sugarcane tops has very less amount of soluble sugar due to which its fermentation is very difficult for silage making, so additives act as a boon for it. Additives are natural or it can be industrial products added in small amount to the forage.The purpose for using silage additives to the silage is to ensure that the growth of lactic bacteria predominates during the fermentation process and also additives reducing losses and improving silage stability, to prevent certain types of fermentation (Clostridial fermentation). Some silage additives have been used to improve the energy recovery and nutrient amount in silage; it will increase the animal performance, and increasing milk production. It is important to ensure that silage additives cannot make poor quality forage into good silage but they can help make top quality forage into excellent quality silage. Sugarcane tops are deficient in true protein and various minerals and also have low energy value and can fulfilled the maintenance requirements of cattle. Silage of sugarcane tops treated with various additives showed some good results in feeding of dairy buffaloes.
Many different silage additives are present in market and are used for, to improve silage quality .It includes like fermentation stimulants, fermentation inhibitors, aerobic deterioration inhibitors, nutrients and absorbents .Their main functions are to either increase nutritional value of silage or improve fermentation process so, losses are reduced which occurs during storage of silage. Silage additives are added to the forage or crop at ensiling, may improve the ensiling (fermentation) process, reduce losses, reduce aerobic deterioration (by using acetic acid) at feed out, limit secondary fermentation, and improve aerobic stability. Additives increase the nutritive quality of the silage, as the result increase animal production and give the farmer a return greater than the cost of the additive.
Biological inoculants are two type, homo and hetro fermenter .Homofermentative inoculants contain bacteria such as Lactobacillus plantarum, Lactococcus Pediococcus and other species. They actively encourage the rapid fermentation and producing mainly lactic acid and bring the pH down to 4 rapidly, stop the further breakdown of the sugar and protein in the sugarcane tops.The addition of Lactobacillus plantarum as a inoculants during ensiling it ensure rapid and vigorous fermentation that results in faster accumulation of lactic acid, lower pH values at earlier stages of ensiling, and improved sugarcane tops conservation. Heterofermentive lactic acid bacteria belonging to, Lactobacillus buchneri, Lactobacillus fermentum and Lactobacillus brevis. Lactobacillus fermentum is a hetero-fermentative bacteria, ferment sugar to a mix of lactic and acetic acid plus carbon dioxide and water. Lactobacillus fermentum can also undertake a secondary fermentation converting lactic to acetic acid and acetic is responsible for aerobic stability of sugarcane top silage. Synergistic effects of bacteria inoculants in combination was evident for a reduction in acetate concentrations and increase of LABs count than those were single bacteria used and they improve the silage quality ,as well as reduce the pH.
Enzyme treatment has been improved microbial growth on feed substrate or to improve the fiber degradation in the rumen. Forages treatment by using enzymes may improve digestibility via a number of different mechanisms like, direct hydrolysis, improvements in palatability, changes in gut viscosity, and changes in the site of digestion. Cellulases or xylanases are two important enzymes which are commonly used in silage.They degrade plant cell walls into sugars. Sugars released by the enzymes, increase growth of Lactic acid bacteria and, fibre degrading enzymes also increase forage digestibility, in some cases. Fibrolytic enzymes degrade the cell wall at a faster rate and extra WSC would be pooled to provide fermentation substrate for LAB growth.
Ensiling process
Silage is highly susceptible to mold and spoils because of moisture and exposure to air or silage is forage preserved in succulent conditions by partial fermentation in an airtight container .Ensiling is an act of preservation under anaerobic conditions. On ensiling epiphytic microbes will undergo competitive inhibition for nutrient and space and fermentation end product will produce on account of dry matter losses. Lactic acid bacteria utilize water-soluble carbohydrates as a nutrient for growth and produce carbon dioxide, lactic acid, and acetic acid during anaerobic fermentation. Acids will reduce the pH content of the ensiled material and inhibit harmful bacteria.
Different Phases of the ensiling process
Ensiling is a forage preservation method based on impromptu lactic acid fermentation under anaerobic conditions. The epiphytic lactic acid bacteria ferment the water-soluble carbohydrates into the lactic acid, and slightly to acetic acid. Due to the production of these acids, the pH of the ensiled material decline and spoilage microorganisms are reduced because of pH. The conversion of fresh forage to silage (ensiling) passes through 4 phases of fermentation which are completed within 21 days of ensiling. Once the fresh material has been stacked and covered to exclude air, the ensiling process can be divided into 4 stages-
Phase 1, the aerobic phase
The first phase is known as the aerobic phase. This phase can take place only in the presence of oxygen. Furthermore, protease and carbohydrates is plant enzyme and they are active in this phase provided the pH is still within the normal range for forage juice (pH 6.5-6.0). When sugar reacts with oxygen is converted into carbon dioxide, water, and heat. The primary aim is to reduce oxygen as soon as possible. The amount of oxygen in silage depends on the storage structure, packing adequately by even distribution of silage, chopping of forage at proper particle length, and dry matter of crop.
Phase 2, fermentation phase
This phase is also identified as the fermentation phase because in this fermentation occurs and pH decline. This phase starts when the silage becomes anaerobic, As the supply of oxygen reduced the anaerobic bacteria grow rapidly. It continues for several days to several weeks, depending on the properties of the ensiled forage crop and the ensiling conditions.
Phase 3, stable phase
This phase is also known as air prevented stage. Most microorganisms of phase 2 slowly decrease in numbers. In this period, some acid-tolerant microorganisms survive others such as clostridia and bacilli survive as spores. When WSC has been completely used, and microbes start to consumed lactic acid as a substrate for secondary fermentation and produce acetic acid, ethanol, and butyric acid. Secondary fermentation occurs when sugar is insufficient or forage contaminated by soil. A particular type of undesirable bacteria converted lactic acid into butyric acid, a weaker acid, so pH increases. Some clostridia also break down the amino acid and produced a high level of ammonia, DM loss, and unpleasant odour.
phase 4, feed-out phase or aerobic spoilage phase
Spoilage begins when silage gets exposed to air. The spoilage process can be divided into two stages- The onset of deterioration is due to the yeast and occasionally acetic acid bacteria which degrade preserving organic acids. This will cause a rise in pH, and thus the second spoilage stage is started, when spoilage microorganisms like bacilli activated and the temperature of silage increased.
The last stage also comprises the activity of many other aerobic microorganisms (facultative) such as molds and enterobacteria. Silages that are opened and exposed to air, aerobic spoilage occurs. The numbers and activity of the spoilage organisms in the silage, determine the rate of spoilage. Due to nutrient degradation and the growth of toxic organism the DM loss was higher in this phase. Aerobic stability of silage was improved when lactic acid converted into acetic acid. To avoid deterioration, it is important to control and optimize each phase of the ensiling process. In phase 1, the amount of oxygen present between the plant particles in the silo can be minimized by using good silo filling techniques. The ensiling process during phases 2 and 3 is more difficult to farmer and can not actively control. Methods to improve phases 2 and 3 are consequently based on the use of various type of silage additives that are already applied at the time of ensiling. Silage additives suddenly reduce the pH of silage and produced more lactic acid. Additive can reduce the all losses and improve the sugarcane tops silage quality. So, additives combination that is most promising like’s lactobacilli and enzymes can enhance the quality and fermentation characteristics of sugarcane tops silage.
https://www.pashudhanpraharee.com/silage-preparation-for-dairy-animals/
https://www.sciencedirect.com/science/article/pii/S0022030218303230
