Effect of Storage Period on Physical, Sensory and Mechanical Characteristics of Green Fodders Pellets, Dry Fodders Pellets and Concentrates Pellets

The livestock industry serves as a pillar for food security, human nutrition and economic growth (Shapiro et al., 2015).  The livestock sectors and animal husbandry occupy a major part in small and marginal farmers economy and contribute 16% of small farm income (Ghosh et al., 2013). Areas of high livestock husbandry have lower poverty rates (Birthal and Taneja, 2012). India is blessed with largest livestock sector and has 20% of world livestock population. As per the 20^th census, the total livestock population was about 535.82 million which accounts for 4.6% increase over 19^th census (DAHD, 2019).  The three primary sources of fodder in India are green fodders, crop wastes and fodder derived from grasslands and grazing area but, there is a huge gap between fodder availability and fodder requirement. India now has a net deficit of concentrates of about 44%, dry fodder of 23.5% and green fodder of 63.5% (IGFRI Vision, 2050). The land accessible for fodder crops has been shrinking every year as a result of heavy demand on the production of food and commercial crops, decreasing soil fertility, unpredictable rainfall and water scarcity. The increasing animal population over years has also widened the gap further. During lean period the farmers are facing challenges in providing adequate quantity of feed and fodder to their livestock, which poses a major threat in sustaining/ improving livestock productivity. The animal feed pelleting is important for increased the feed efficiency. Fodder pelletisation technique is the production of fodder pellets by using different resources of green fodders, dry fodders and concentrates. Fodder pelletisation, helps to meet out the fodder requirement during winter and dry period and it also helps to meet out the adequate feed supply to livestock during lean period.  Fodder pellet production helps to prevent the fodder wastage, eliminates the harmful pathogen and increases the nutrient utilization and improves the animal acceptability (Manasri et al., 2012). Reduction of feed wastage by animal through fodder pelleting and it helps to ensures the homogeneity of feed and fodder thereby the feed conversion rate has been increased by 4-6% (Torres et al., 2013 and Huawei et al., 2015).  The pelleting of poor quality forages like non-conventional fodder, crop residues, crop secondary products could be improved by value added with additives like molasses, bran, minerals, jaggery and salts added with pellets and it increased the nutritive content and improved the animal acceptance through palatability (Gulecyuz et al., 2016).  The primary factor used to determine the storage life of fodder pellets depends on their physical, sensory and mechanical characteristics. The good physical (colour and odour) and sensory characteristics (mould) are indicators of the quality of pellets and it determines the animal acceptance as well as marketability of the pellets.

The experiments were conducted at Forage Pelleting Unit, Department of Forage Crops in Agricultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu  from December 2020 to June 2022 to identify the best suitable fodder crops for fodder pellets production. Based on the availability, the green fodders, dry fodders and concentrates were identified for quality pellet production. The three laboratory experiments were conducted and laid out in completely randomized block design (CRD) with three replication. In the first experiment consisted of 13 different category of green fodders from grass fodders, cereal fodders, legume fodders and tree fodders  viz., G₁: Bajra Napier hybrid, G₂: Guinea grass, G₃: Cenchrus grass, G₄: Fodder sorghum, G₅: Fodder maize, G₆: Fodder cumbu, G₇: Lucerne, G₈: Hedge lucerne,  G₉: Fodder cowpea, G₁₀: Agathi, G₁₁: Moringa, G₁₂: Gliricidia, G₁₃: Subabul were selected for pellet production. In the Second experiment, different type of dry fodders were collected from the field after the harvest of economic products. The dry fodder used for pellet production are D₁: Rice straw, D₂: Maize stover, D₃: Maize husk, D₄: Sorghum stover, D₅: Ragi straw, D₆: Pearl millet stover, D₇: Wheat straw, D₈: Groundnut haulms, D₉: Groundnut shells, D₁₀: Sugarcane tops, D₁₁: Blackgram husk. In the third experiments, different concentrates were used for pellet production. They are, C₁: Maize grain, C₂: Sorghum grain, C₃: Cotton seed oilcake, C₄: Groundnut oilcake, C₅: Sesamum oilcake, C₆: Coconut oilcake, C₇: Sunflower oilcake, C₈: Rice bran, C₉: Wheat bran. In above three experiments, the selected green fodders and dry fodders were harvested with the help of fodder harvester cum chaffer. The chaffed material was then dried using a solar drier at 70°C for three to four days for attaining the ideal moisture of 12%. Then, dried material were grinded by fodder pulverizer and the pulverised material was conveyed through conditioning with passing the steam at 60 to 70°C. Then, the conditioned material was passed through a pelletizer with 6 mm die diameter.
       
The observation on storage parameters of physical, sensory and mechanical characteristics of green fodder pellets, dry fodder pellets and concentrates pellets were recorded. The pellet durability index significance level (P<0.05) was assessed by using OPSTAT software and then difference between means were ranked by using Duncan’s new multiple range test (Duncan, 1955).
 
Physical and sensory characters of fodder pellets
 
The physical and sensory characters of fodder pellets are the key factor used to determine the storage life of fodder pellets for animal acceptability as well as market accessibility. Based on the nature of the pellets, the physical characters (colour and mould) and sensory character (odour) was noted at regular intervals from day of pellet production (0 DAP), 60 DAP, 120 DAP and 180 DAP.  The individual fodder pellets colour is noted, mould is classed as present or absent and odour is noted as pleasant, favorable and unfavorable as observed at 0 DAP, 60 DAP, 120 DAP and 180 DAP.
 
Mechanical character of fodder pellets
 
Pellet durability index is used for determining the pellet quality and it is the measure of pellet resistance against fragmentation and impact forces. High quality pellets can be defined as pellets that can endure repeated handling as during bagging, transportation, storage and moving on feed lines without excessive breakage or generation of fine particles. The durability of pellets can be assessed by using a tumbling can device.  For this, 10 grams of individual feed pellets were first sieved to remove any small particles and the samples were tumbled for 10 minutes at 50 rpm. The samples were immediately sieved with a 5 mm sieve for around 30 seconds to remove fine particles and determine the percentage of intact feed samples.
       
The PDI was computed as per the procedure of ASAE Standards (2003).

Physical and sensory characters of fodder pellets
 
In this study, the physical characteristics such as colour and mould were noted and are presented in Table 1. Green, dark green, light green, greenish brown and light brown were the colors of green fodder pellets as given in Table 1 and Table 1a. Dark brown, light brown, black, light yellow and greenish are the colors of dry fodders pellets and are given in Table 2 and Table 2a, while brown, dark brown and blackish brown are the colors of concentrates pellets and are given in Table 3 and Table 3a.  The physical and sensory characters (colour, odour and mould) are indicative factor for the pellets of excellent qualities. Odour is an important physical characteristic in terms of pellets acceptability. Regarding green fodder pellets, all the green fodder pellets were characterized by pleasant odour with no indication of putrefaction. Meanwhile, the Agathi pellets (G₁₀) were affected with unpleasant odour as the storage period increased.  Regarding dry fodder pellets and concentrates pellets, the same colour as from the date of pellets production was maintained in all the dry fodder and concentrates pellets. Regarding the odour, freshly prepared dry fodders pellets  and concentate pellets were registered with pleasant and favourable odour. As the time increases, the odour became unpleasant only in pearl millet straw pellets (D₆)  among the dry fodder pellets and sorghum grain pellets (C₂) among the concentrate pellets at 120 DAP and 180 DAP.  This finding was supported by  Ojo et al., (2019).
 

 

 

 

 

 

 
Mechanical characteristics of fodder pellets
 
The mechanical characteristics of fodder pellets is Pellet Durability Index and assesses a pellet’s resistance to impact and fragmentation forces, is used to assess its quality. When a pellet’s PDI is high, it indicates that it is stable, Whereas low PDI indicates that the stability of the pellets is weak.
       
In experiment 1, the individual green fodder pellets PDI were observed and presented in Table 4. The Pellet Durability Index (PDI) ranged from 88.1 per cent to 99. 3 per cent.  Among green fodder pellets, the G₈- Hedge lucerne pellets has recorded highest percent of PDI which recorded with 99.3 % when compared with all other treatments and it was on par with G₁- Bajra Napier hybrid grass,G₃- Cenchrus grass, G₄ -Fodder sorghum, G₈-Hedge lucerne , G₉ -Fodder cowpea, G₁₀- Agathi,  G₁₁- Moringa and G₁₃- Subabul and it suggests that the pellets are more stable. This might be due to that protein, lignin, starch and fat are the natural biomass binders that can be activated under high pressure during the pelleting process. These binders aided to bind the particle together and increase the durability of the pellet (Kaliyan 2008). Whereas, high-fiber feedstuffs are difficult to agglomerate into pellets, resulting in low durability (Cavalcanti et al., 2005). This was confirmed by Hansen and Storebakken, (2007).
       

 
In experiment 2, the different dry fodder pellets PDI were observed and presented in Fig 1. Among dry fodder pellets, D10-sugarcane top pellets had recorded highest PDI  which registered with 99.4% than all other treatments. Least PDI was recorded in D6- cumbu stover pellets  with 93.2%.  The natural biomass binders that can be activated under high pressure during the pelleting process include protein, lignin, starch and fat. These binders helped to hold the particle together and improved the pellet’s durability. According to Colley et al., (2006), pelletization techniques significantly increased the bulk density of corn stover, ground switch grass, sorghum stalk wheat straw and of about 6-10 times higher than before pelleting.  This was confirmed by Stevens (1987) and Winowiski (1998).
               

 
In experiment 3, the different concentrate pellets PDI were observed and given in Fig 2. The highest PDI in concentrated feed was recorded in C₂- sorghum grain pellets and least PDI was recorded in C₉ -wheat bran pellets (97.1%). This might be due to preheating in the presence of moisture  softens the natural binders in the biomass, such as starch, lignin and protein, prior to pelletization, resulting in more durable pellets. This increase in moisture with increase in durability might be due to binding of water molecule that strengthened the bonds between individual particles in the pellets as suggested by Fasina (2008). Stevens (1987) and Winowiski (1998) compared the pellet durability of corn-containing diets which was replaced with wheat.
 

Based on the findings of this experiment, Bajra Napier hybrid grass and Cenchrus grass among the grassy fodders, Fodder maize and Multi cut fodder sorghum among the cereal fodders, Lucerne and Hedge lucerne among the legumes and Agathi and Moringa  among the tree fodders are identified as the best suitable green fodder crops for cost effective quality pellet production. Whereas, maize stover, groundnut haulm, finger millet straw, sugarcane tops, maize husk, black gram husk are found to be suitable dry fodder substitutes for cost effective quality pellet production. While, maize grain and sorghum grain, rice bran, groundnut oil cake, coconut oilcake and cotton seed cake-among the concentrates are found to be suitable additives for cost effective quality pellet production.

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