Effect of pellet mill and binder on durability and economics of production of Cassava-Gliricidia pellets

O A Dada and O A Olorunnisomo¹

Animal Production Unit, Adeyemi College of Education, Ondo, Nigeria
doluwagbemiga@yahoo.com
¹ Department of Animal Science, University of Ibadan, Ibadan. Nigeria

Abstract

The study was carried out to assess the effect of pellet mill and binder on economics of production and quality characteristics of pellets made of cassava root and gliricidia leaf. Two flat die pellet mills (vertical and horizontal designs) at 2 levels of starch inclusion (0 and 5%) were adopted for the pellet feed production. The effect of pellet mill and starch inclusion was significant on the assessed quality parameters. The crude protein content of pellets ranged from 17.65 to 19.45%. Physical quality was measured in terms of durability. Pellet Durability Index values show that pellets compressed by vertical design mill with 5% starch are the most durable. The cost of pellet production ranged between 39.3 and 41.0 dollar per 100 kilogram of pelleted feed. This is considered affordable and economical when compared to conventional finished feed employed in poultry production. It is concluded that cassava root meal and gliricidia leaf possess the potential of solving the problem of limiting feed resources of ruminant animals during period of drought and can be pelleted without the inclusion of binder.

Key words: cassava root, leaf meal, quality, ruminant

Introduction

The unavailability of sufficient pasture forage during the dry season in tropical and subtropical regions is a major problem in ruminant livestock production (Olorunnisomo, 2011). During this period, grazing ruminants lose weight and in extreme cases some deaths do occur. This is the plight of herdsmen in the semi- arid/arid zones of the country. Therefore, there is the need to develop sustainable alternatives to meeting the nutritional requirements of these animals during the period of scarcity. These alternatives should also take into consideration the technical, economic and social aspects of the problem. This will also entail developing means capable of optimising the use of indigenous feed resources such as cassava.

In Nigeria, cassava production is well-developed as an organized agricultural crop. It has well-established multiplication and processing techniques for food products and cattle feed. Nigerian cassava production is by far the largest in the world; a third more than production in Brazil and almost double the production of Indonesia and Thailand (FAO, 2004a). Recently, the world cassava production stands at 291 million tonnes (FAOSTAT 2019) with 70% of the total production being concentrated in five countries, namely Nigeria, Congo Democratic Republic, Thailand and Indonesia. Africa is regarded as the world largest cassava growing region with a production of 177 million tonnes in 2017 and Nigeria remained unarguably the highest producer of cassava in the world with about 59 million tonnes in 2017. To a limited extent, it is used as a livestock feed, particularly in non-ruminant diets. Ruminants can be fed on cassava root, foliage, peel and residue obtained after processing cassava. Research has shown that tubers and peel are good energy sources, which when well-fortified with nitrogen, minerals, vitamins, and roughage, promoted positive and high performance levels in dairy and beef cattle, sheep, and goats (Losada and Alderete, 1979; Okeke and Oji, 1988)

Moreover, as part of global efforts to improve animal nutrition during this critical period of the year, attention is being shifted to the evaluation of indigenous multi-purpose tree (MPT) species such as Gliricidia, Leucena, moringa and others. These indigenous MPT are well distributed and adapted to the hot tropical climate (Anele et al, 2006). The current utilization level of these indigenous MPT is still low compared with their potentials. The feeding of such supplemental protein diets is one of the means of minimizing weight loss during this period of drought. Gliricidia is one of the major tropical forage trees due to its high protein content and nutritive value. It can be cut by hand and left on the ground for grazing or carried to paddocks or stalls. Gliricidia is generally used as a high protein supplement to low quality basal feeds such as grass, straw and other crop residues.

One of the means of preserving excess forage in order to ensure a steady supply of quality feeds for livestock during the dry season is to make the leaf meal into pellets. These pellets can be improved nutritionally by mixing leaf meal with other feed ingredients such as wheat bran, cassava tubers, palm kernel cake, brewers’ dry grain, and etc. Pellets have a number of advantages over mash feed because conditioning of the formulation mix can improve the palatability and digestibility of the feed, resulting in improved performance. It is however important to consider the cost of producing the pellets and the durability since the aim is to commercialize the process and make it available to farmers that mostly reside in the interiors notable for bad roads.

Materials and methods

Experimental location

The experiment was conducted at the Dairy Unit of the Teaching and Research Farm, University of Ibadan, Ibadan, Nigeria (3º45´E, 7º27´N; at 220m above sea level). Annual rainfall ranges from 1150 - 1500mm.

Processing of cassava root meal and gliricidia leaf

Gliricidia leaves were harvested from the existing plantations at the Teaching and Research Farm (TRF).The leaves were removed from the stem and air dried to reduce the moisture level and thereafter bagged. It was then milled at the feedmill of the TRF, University of Ibadan with a hammer mill having 2mm sieve. Cassava roots was purchased from Ikire in Osun state. It was washed and grated together with the peel. It was thereafter pressed, dried and finally milled into flour using sieve of 2mm diameter. Other ingredients were purchased from the feedmill unit of the Teaching and Research Farm, University of Ibadan. They were mixed and pelletized.

Proximate Analysis

Feed sample (Pellets) were analysed for Dry Matter (DM) and Crude Protein (CP) according to AOAC (2005). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined according to the procedure of Goering and Van Soest (1985).

Durability Measurement

The durability of the pellets was evaluated by using a durability tester. 100g of each sample was placed in a tumbling box having 60 rpm (revolution per minute) and was allowed to run for 5 minutes. The samples were recovered and the fines were separated from the pellets.

Statistical Analysis

The data collected were subjected to analysis of variance (ANOVA) using the General Linear Model (GLM) procedure of SAS/STAT^® software, version 9.1 Significant differences among means were separated using the Duncan’s Multiple Range Test (DMRT) of the same software.

Photo 1. Horizontal design flat die pellet mill Dairy unit, Teaching & Research Farm, UI	Photo 2. Vertical design flat die pellet mill Feedmill Unit, Teaching & Research farm

Results and discussion

The CP content of pellets ranged from 17.65 to 19.45%. All these values are well above 8% suggested by Norton (1994) for effective ruminal function. This is an indication that pellets of this composition can serve as a protein supplements for cattle, especially during the period of drought.

Pellet Durability Index

The effect of pellet mill and binder on the pellet durability index (PDI) value was pronounced with pellets compressed by vertical design mill having lesser fines after agitation compared to pellets from horizontal design. The difference may be due to the quantity of steam generated by the individual pellet mill. Skoch et al. (1981) indicated that steam conditioning improved pellet durability. The addition of starch binder (5%) made the pellets to be more durable. PDI values for pellets having binder were significantly (P < 0.05) higher than pellet without binder. This result emphasized the importance of binder in the production of durable pellets. However, pellets without binder compressed by vertical design mill were more durable than pellets from horizontal design mill irrespective of binder inclusion. This indicates the great influence of pellet mill on durability of pellets. Sonthi and Nitipong (2013) studied the potential of cassava root to serve as pellet fuel and found out that all pellets had little amount of fines. This result agrees with the above assertions and show that pellets of cassava roots are of good durability. In addition, the durability of such pellets can however be improved upon through the addition of binders. This will be necessary in sub-saharan Africa where there are quite a number of bad roads capable of causing serious agitation when feeds are being transported. However, the results suggests that when pelleting a starch rich feed ingredient, the ability of mill to generate adequate steam is of more importance and a determining factor of durability.

Economics of production

It is imperative to consider the cost implication of producing each pellet since it is the aim of this study to develop a nutrient supplement that is both affordable and sustainable. The cost analysis is presented on table 4. The cost of pellet production ranged between 39.3 and 41.0 dollar per 100 kilogram of pelleted feed. Diet 1 (pellets compressed by vertical design flat die pellet mill without starch) has the lowest cost of production, while diet 4 (horizontal design flat die pellet mill) was the most expensive to produce. The cost of binder (cassava starch) was responsible for the relative increase in cost of producing diets 2 and 4. Cassava starch is quite expensive compare to buying cassava root meal of the same quantity. This might be attributed to other industrial uses of starch. Moreover, the cost of pelleting feed on the horizontal flat die pellet mill is judged to be higher than that of vertical design flat die mill. This is because the horizontal design pellet mill runs on diesel fuel. However, this might be a plus on the long run considering the situation of power in Nigeria.

Conclusion

• That pellets made from cassava root meal and gliricidia leaves possess the potential of solving the problem of limiting feed resources in sub Saharan Africa.
  
  
• The efficiency of pellet mill must be carefully considered for optimum maximization of these resources.
  
  
• It is recommended that binder inclusion in cassava-gliricidia pellets should not exceed 5% of the total feed composition.

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