Development of moringa multi-nutrient block as a dry season feed supplement for ruminants

V O Asaolu

Department of Animal Nutrition and Biotechnology, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso, Oyo State, Nigeria
voasaolu@yahoo.com

Abstract

The study was carried out to establish optimum protocols and conditions for making moringa multi-nutrient blocks (MMNB) considered suitable for on-farm adoption by ruminant farmers in terms of hardness, compactness and cost, while aiming at nutritional complementarity among the different ingredients. 8 formulae were assessed alongside a formula (control) developed at the International Trypanotolerance Centre (ITC), Banjul, The Gambia, from wheat offals, moringa leaf powder, urea and salt, with cement as the binder. Wooden moulds, measuring 13×13×10 cm each, were used to cast the MMNBs. The blocks were assessed for hardness and compactness over 7, 14 and 21 days. MMNBs from the control group, and the two selected promising formulae on the basis of physical characteristics, were separately sampled, pulverized and analyzed for proximate and mineral contents. Metabolizable energy (ME) contents of the control and selected structurally-stable MMNBs were predicted. The cost implications of block formulation for the different formulae were done using the prevailing market ingredients’ prices in the Nigerian Naira (N). 10 MMNBs (mean weight; 1.00±0.05 kg), when dry, were produced from each 10.0 kg mixture, and 6.50 litres of water were found optimum for mixing.

The most desirable MMNBs were produced from a formula containing 37.0% wheat offals and 35.0% moringa leaf powder, with cement inclusion at 15.0% as the binder. Lime powder, urea and salt inclusions were 5.00% each. MMNB dry matter levels were high (86.0 – 88.2 %). The CP varied between 18.4 and 22.0 %, while the predicted ME values were between 14.3 and 14.4 MJ/kg DM. Ca, Mg, Zn and Cu levels were higher than the critical levels for goats. The unit price of the most structurally-stable multinutrient blocks was N29.4, about half the price of a conventional concentrate mixture (w/w). The potentials and prospects of the formulated moringa multinutrient blocks as dry season feed supplements in ruminant nutrition appear quite promising, with possibilities of on-farm adoption due to the simplicity in its production technology.  

Keywords: block hardness and compactness, cement, salt and water mixing ratio, urea

Introduction

In Sub-Saharan Africa, the dominant feeding systems for ruminants are based on grazing, usually on communal lands (Leng et al 1991), crop residues and agro-industrial by-products (Tchinda et al 1993; Akter et al 2004). Leng et al (1991) observed that the nutritive value of grasses on communal lands is not a constraint when there is rain. However, during the usually extended dry seasons, the grasses, crop residues and agro-industrial by-products are usually fibrous, low in digestibility and devoid of most essential nutrients including fermentable nitrogen, digestible by-pass protein, minerals and vitamins which are required for increased rumen microbial fermentation and improved performance of the host animal (Dixon and Egan 1988; Leng et al 1991; Osuji et al 1995). They often contain below the minimum metabolizable energy content regarded as being useful (Leng 1989). Animals resultantly suffer weight losses, lower birth weights, lowered resistance to diseases, and invariably, reduced reproductive and productive performances (Onwuka et al 1989; Leng et al 1991; Bamikole and Babayemi 2004). 

Feed supplementations with concentrate mixtures including cereal grains, cereal brans, or oilseed cakes have resulted in increased intakes with concomitant improved animal performance in intensive production systems, and have been the subject of several excellent reviews including that of Bangani et al (2000). Unfortunately, these supplements are often not fed due their unavailability and their high costs (Nouala et al 2006), thus making them too expensive for small-scale farmers. The preference to export these materials for foreign exchange was identified by Sansoucy and Hassoun (2007) as one of the factors for their non-availability and high costs. The same scenario has been observed by the same authors to also exist with mineral and vitamin supplements. The use of fodder trees as supplements has been suggested as an alternative to the use of concentrates (Jones 1979; Ndemanisho 1996; Roothaert and Paterson 1997). The forages from these trees contain reasonable amounts of protein, both as soluble and insoluble components, and are also an important source of minerals such as sulphur, copper and iron (Dixon and Egan 1987; Somasiri et al 2010a). The availability of fodder trees, with leaves rich in good quality protein, which could be a cheap and suitable solution, has however been observed by Speedy and Pugliese (1992) to be insufficient to cover animal needs. Planting and growing of such trees were described as long-term objectives which should be encouraged wherever possible (Sansoucy and Hassoun 2007). These authors thereafter recommended the provision of supplements containing nitrogen, essential minerals and vitamins as part of the diet, as a shorter-term solution. Formulation of multinutrient blocks based on low cost and locally available feed resources that do not compete with human food has been described as very promising by Makkar (2007) in this regard. Such a feeding strategy is aimed at creating an efficient ecosystem for fermentative digestion of fibre in the rumen; and balancing the products of the fermentative digestion with by-pass (or escape) nutrients of dietary origin in order to optimize the use of the available energy (Preston and Leng 1984).  

Reports abound in the literature on the origin, development, formulation and utilization of feed blocks (Sansoucy and Hassoun 2007; Habib 2004; Mohammed et al 2007; Ben Salem et al 2007; Makkar 2007; Asaolu 2009; Aye and Adegun 2010; Somasiri et al 2010a; 2010b) from various locally available materials, with and without molasses. Asaolu (2009) reported on the development, formulation and utilization of moringa multi-nutrient blocks (MMNB) in The Gambia and Sierra Leone, as part of an International Development and Research Centre (IDRC)-sponsored Research and Development programme that was executed by the International Trypanotolerance Centre (ITC), Banjul, The Gambia, over a period of about 12 years; 1998 to 2009.  The MMNB was a novel approach developed at ITC to improve the protein, energy and mineral nutrition of ruminants, particularly during the extended dry season in The Gambia; a country classified as a semi-arid zone in agro-climatic terms (Bourn et al 2001). The components of the MMNB and their percentage incorporation levels, as developed at ITC, comprised of moringa leaf powder (25.0 %), rice bran (32.0%), lime powder or crushed oyster shell (15.0%), urea (8.00%), table salt (5.00%) with cement (15.0%) as a binder. In an on-farm demonstration of the benefits of MMNB in the nutrition of small ruminants in the Western Region of The Gambia (Asaolu et al 2010), mean growth rates of 28.0 g/day and 35.0 g/day were observed for the experimental bucks and rams that were offered daily supplements of MMNB between March and June 2008, a period corresponding to the peak of the dry season in the country. Reliable animal block intake figures could not obtained due to poor block handling by the participating farmers, apparently due to the less-than-satisfactory hardness of the blocks. Observations showed that intakes could have been over-estimated. The probable danger of animals consuming the MMNB too rapidly due to their less-than-satisfactory hardness was however not lost to the researchers, with the likely problem of urea toxicity. The need to establish a sound physical structure of MMNB therefore became imperative.  

At least, 60 countries are now using the multinutrient technology as a strategic supplement for ruminants, mainly cows, sheep and goats raised under harsh conditions (Ben Salem et al 2007). The use of multinutrient blocks as supplements to poor-quality basal diets for ruminants is however new in Nigeria (Mohammed et al 2007), while efforts are currently being made to bring Moringa oleifera to national consciousness in the country through fora such as the First National Summit on Moringa Development organized by the Raw Materials Research and Development Council at the federal capital of Abuja in October 2010 (Asaolu et al 2011). This study was therefore conducted to establish the optimum protocols and conditions for making moringa multi-nutrient blocks considered suitable for on-farm adoption by ruminant farmers in terms of desired hardness, compactness and cost, while aiming at a nutritional complementarity among the different ingredients. 

Materials and methods

Experimental site 

The study was conducted at the Teaching and Research Farm of the Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria, in March 2011, which coincided with the peak of the dry season in the area. The area is a fire sub-climax of the rain forest, referred to as the derived savanna, and is characterized by extensive grasslands interspersed with a few tree species such as locust bean, shear butter, kolanut and oil palm (Hopkins 1974; Chedda and Crowder 1977). The area is situated at about 600 m above sea level, and located on Latitudes 8^o 07¹ N and 8^o 12¹ N and Longitudes 4^o 04¹   and 4^o 15¹ E (Oguntoyinbo 1978).  Ogbomoso has a maximum temperature of 33^oC and a minimum temperature of 28^oC. The humidity of the area is high (74%) all year round except in January when the dry wind blows from the north, and the annual rainfall is over 1000 mm (Olaniyi 2006). 

Ingredients and ingredient mixing 

Eight (8) different moringa multinutrient block formulae were assessed alongside the formula developed at ITC (Control treatment) from wheat offals, moringa leaf powder, lime powder, urea and salt; with cement as the binder (Table 1).

Moringa leaf powder was prepared from moringa leaves harvested from an established plot at the University Teaching and Research Farm after a cutback period of 60 days after the first rains of 2011 in the month of March. The leaves were air-dried to a constant moisture level under a shed for periods ranging from 8 to 14 days, and all the stalks were thereafter separated and discarded. The dried leaves were subsequently milled using a commercial hammer mill. The other ingredients were purchased from a reputable livestock feed/feed ingredients’ store in Ogbomoso.

All the blocks were prepared manually from a total of 10.0 kg of the respective ingredients for each formulation (Table 1). The mixing procedures for the various experimental moringa multinutrient formulae are described as follows:

Control moringa multinutrient blocks

In line with the protocol developed at ITC (Asaolu 2009), moringa leaf powder, wheat offals, lime powder and cement were measured and mixed. Water was added to the mixture to make it moist. The urea and salt were dissolved in 5.00 litres of water, and the resulting water/urea/salt mixture was added to the first mixture and stirred by hand. Additional water was added as necessary.

MMNB formula I 

Wheat offals, moringa leaf powder and lime powder were measured and mixed together, with enough water added to make the mixture moist (Mix 1). Urea was measured and dissolved in water (Mix 2) while salt and cement were measured and mixed with water at the ratio of 1:2 as recommended by Aye and Adegun (2010) (Mix 3). Mix 2 was added to Mix 1 to form a paste (Mix 4), and Mix 3 was subsequently added to Mix 4. Enough water was added to form a homogenous semi-solid mixture (Mix 5) which was ready for moulding.

MMNB formulae II, III, IV, V, VI, VII and VIII

The measuring and mixing procedures were as described for moringa multinutrient block formula I, but with varying ingredient ratios as indicated in Table 1.

Moulding and drying 

Wooden moulds, measuring 13×13×10 cm each, were used in casting the moringa multi-nutrient blocks. During casting, the insides of the moulds were lined with nylon sheets to prevent the blocks from sticking to the walls of the moulds, and to allow for easy removal of the blocks from the moulds (Onwuka 1999). Moulding was done under a roofed open-sided building, a drying method which simulates the drying conditions that prevail in rural areas where a lot of small ruminants’ production activities take place (Onwuka 1999). The floor was sprinkled with wheat offals, so that the blocks would not stick to the floor. Each mix was then pressed separately into moulds and the blocks were made on the floor. The blocks were compressed manually using foot pressure with flat wooden slabs measuring 33 × 17 cm constructed for the purpose. Moulds and nylon sheets were removed sequentially from the blocks immediately after moulding. The blocks were left to air-dry in the well-ventilated shed.

Assessment of block hardness and compactness

The blocks were monitored and assessed for hardness and compactness over 7, 14 and 21 days respectively. These were done by three persons independently using a subjective scale: Soft (+), Medium (++) and Good (+++). Hardness was determined by pressing with the thumb in the middle of the block while compactness was measured by the ease to break the block by hand (Mohammed et al 2007).

Nutrient and mineral characterization 

About 50.0 g representative sample from each multinutrient block from the control group, and each of the selected promising formulae on the basis of physical characterization, were separately pulverized, pooled together and sampled for their respective proximate contents using the standard methods of AOAC (2000).  Mineral analysis was by wet digestion of sample in HNO₃/HClO_4. Ca, Zn, Mg and Cu contents were determined with the aid of an atomic absorption Spectro-photometer. The major ingredients (moringa leaf powder and wheat offals) that were used in the formulation of the moringa multinutrient blocks were similarly analyzed for proximate and mineral contents (Table 2).

All analyses were done in duplicates. Metabolizable energy (ME) contents of the control and selected structurally-stable multinutrient blocks were predicted from the equations of Abate and Meyer (1997); ME (MJ kg⁻¹ DM) = 5.34 − 0.1365CF + 0.6926NFE − 0.0152NFE² + 0.0001NFE³; R² = 0.45, P < 0.0001.   

Cost implication analysis 

The cost implications of moringa multinutrient block formulation for the different formulae were done using the prevailing prices of the various ingredients in the Nigerian Naira (N) at the time of the study. Thereafter, a conversion factor of N155 to $US1.00 that was prevailing in the open market at the time of the study was used.  

Results and discussion

Moringa multinutrient block ingredients: their inclusion levels and chemical compositions 

The experimental moringa multinutrient block formulae are as contained in Table 1 while Table 2 contains the chemical compositions of the major ingredients that were used in making the blocks.

10.0 kg formula mixtures were evaluated with moulds measuring 13×13×10 cm each. 10 moringa multinutrient blocks with a mean weight of 1.00±0.05 kg, when dry, were produced from each 10.0 kg mixture, with a total of 90 MMNBs resulting from all the formulae (9 formulae × 10 MMNBs). 6.50 litres of water were found to be optimum for mixing MMNBs (Table 1). It resulted into the most homogenous mixtures; causing no water leakage from the blocks, either during moulding when pressure was applied or during the drying process. Multinutrient block moisture content has been reported (Herrera et al 2007) to play a fundamental role in relation to blending, setting and mixture manipulation. The researchers described the water component of multinutrient blocks as a critical agent in achieving a good mixture in the agglutinant and the fibre, obtaining the chemical reactions needed for block hardening.     

The ingredients used in the formulation of multinutrient blocks and their proportions determine their physico-chemical characteristics, and hence affect acceptability and intake by ruminants (Herrera et al 2007). Wheat offals and moringa leaf powder were the major ingredients of the blocks. The inclusion levels of wheat offals ranged from 32.0 to 37.0 % while moringa leaf powder was included in the range of 25.0 to 35.0 %. The wheat offals percentages were comparable to the inclusion levels used in Syria (Hadjipanayiotou et al 1993) and Nigeria (Mohammed et al 2007), with and without molasses and using different formulae. Wheat offal, a combination of “weatings” and bran (Scarr 1987), is a by-product of the manufacture of flour, and is locally available in almost all countries (Ramchurn and Raggoo 2000). Although current statistics could not be obtained, about 382,666 metric tonnes of this by-product were reportedly (Egbunike and Ikpi 1990) produced by registered companies in Nigeria in 1985; demonstrating its relative abundance in the country. Herrera et al (2007) had observed that the stimulus for strategic supplementation with multinutrient blocks in Venezuela savanna was the abundant availability of such fibrous resources that could require a source of fermentable nitrogen. Cereal offals have multiple purposes in blocks. They are high in phosphorus, trace minerals as well as a wide range of vitamins, and also act as an absorbent for moisture, thus giving structure to the block (Sansoucy et al 1988).Wheat offal, arguably the most important cereal offal in Nigeria, also supplies both protein and energy (Scarr 1987). A nitrogen content of 2.78 % (Table 2) translates to a crude protein content of about 17.4% while its high NFE content (59.4 %; Table 2) could be taken as a reflection of its high energy content. Scarr (1987) had reported an approximately 10.0 MJ metabolizable energy and 15.0 % crude protein on a dry matter basis. The leaves of Moringa oleifera are an important component of the block at 25.0 – 35.0 % inclusion levels (Table 1). With nitrogen and NFE contents of 4.28 and 39.6 % respectively (Table 2), moringa leaves could be regarded as potential sources of protein and energy in the resultant moringa multinutrient blocks. Price (1985) described moringa leaves as one of the best plant foods that can be found. It offers a good alternative source of protein to humans and livestock wherever they thrive (Nouala et al 2006). The crude protein of moringa leaves has been reported (Becker 1995) to be of better quality for ruminants, relative to the most commonly-used multipurpose tree leaves, because of their high content of by-pass protein (e. g., 47.0% versus 30.0% and 41.0% for gliricidia and leucaena, respectively). The metabolizable energy of moringa leaves has been reported (Foidl et al 2001; Asaolu et al 2009) to be of similar order of magnitude as for some highly nutritive fresh forages such as alfalfa. Moringa is easy to cultivate, resistant to drought, and the tree produces abundant leaves with reportedly (Price 1985). Many minerals, particularly Ca, P and Na, are essential for ruminants for optimum productivity (Ghazanfar et al 2011). Asaolu et al (2011) reported the Ca, P and Na contents of moringa leaves to be higher than the critical levels that were recommended by McDowell (1985) to cover the requirements of ruminants. Lime powder is expected to complement the expected calcium supply from moringa leaves, as calcium is the most abundant mineral element in the body with about 98.0 % being located in the skeleton (Tessendlo Group 2004). In the skeleton, calcium, together with phosphorus, is used to provide strength to the bones. Salt was added to the blocks to ensure adequate Na supply, although at inclusion rates of 5.00 to 8.00 %, livestock would be deterred from ingesting too much of the block at any given time (Huque and Stem 1994). It also acts as a preservative (Ben Salem et al 2007). Salt is known to contain 39.3 % sodium and 60.7 % chlorine (Mohammed et al 2007). Urea, known to farmers as a fertilizer for crop production, has been traditionally used in making multinutrient blocks for livestock for improving feed digestibility and providing protein (Makkar 2007). Urea contained 45.0% nitrogen (Table 2), which is equivalent to about 287% crude protein and it is rapidly digested by ruminants (SMEDA 2009). Ruminant feed supplementation with urea has been reported to result in a greater feed intake due to a greater supply of ammonia to the rumen microorganisms (Preston 1995; Dong et al 2003). Campling et al (1962) showed that its continuous supply to cattle could increase the intake of straw by about 40.0 % and its digestibility by 8.0 units (or 20.0 %). Together with the energy substrates supplied by moringa leaves and wheat offals for rumen microorganisms, urea would be expected to improve feed conversion efficiency (Xie et al 1997). Inclusion levels varying from 5.00 to 8.00 % were lower than the upper limit of 10.0% beyond which animal poisoning could occur (Yami 2007).

A gelling agent or binder was necessary in order to solidify the blocks. Although the mechanism of gelling is unknown, various products have been tried successfully: magnesium oxide, bentonite, calcium oxide, calcium hydroxide and cement (Sansoucy et al 1988). Cement was used as the binder in this study. The main constituents of ordinary cement, according to Arora and Bindra (1996), are lime and silica with lesser quantities of oxides of aluminium, iron, magnesium, sulphur and potassium and sodium. Aluminium oxide gives cement the "gelling" characteristic which makes it an important ingredient in multinutrient block formulation and preparation. In addition to being a gelling agent, cement has been reported (Mohammed et al 2007) to contain 25.0% calcium, 21.5 ppm iron, 1790 ppm manganese and 130 ppm magnesium. Although the use of cement has raised some questions from various nutritionists and extension workers about possible negative effects on animals (Sansoucy et al 1988), studies conducted in Canada and USA on the utilization of cement and its by-products as minerals for animals did not reveal any negative effect when fed up to 3.00 % of the total daily dry matter intake (Aarts et al 1990). Cement inclusion levels of 15.0 to 20.0 % as investigated in this study are not expected to result in such magnitudes of cement intake. In some earlier studies (Hadjipanayiotou et al 1993; Mohammed et al 2007; Aye and Adegun 2010), cement had served as binders at 10.0 and 15.0 % inclusion levels with no adverse effects observed on animal performance. A 10.0 – 15.0 % cement inclusion level has been described (Yami 2007) as sufficient, with claims that higher levels may make the blocks too hard.

Physical characterization of MMNB 

Physical characterization of multinutrient blocks has been described (Herrera et al 2007) as an important aspect to be considered during manufacture, particularly under artisanal conditions. All the MMNB formulae resulted in blocks of comparable hardness (++) and compactness (++) up till the 14^th day of drying (Table 3). However, on day 21, formulae VI and VII resulted into blocks which were leaf green in colour, and adjudged to be of optimum hardness (+++) and compactness (+++), while hardness and compactness of the blocks resulting from the remaining formulae were observed to remain as they were on day 14 with varying shades of green colour.

Block hardness, expressed as penetration resistance by Herrera et al (2007), is a factor that markedly determines animal intake (Mwendia and Khasataili 1990; Hadjipanayiotou et al 1993; Birbe et al 1994). Herrera et al (2007) observed that as block hardness increases, animal intake diminishes. Onwuka (1999) opined that optimum hardness and compactness of multinutrient blocks indicated that the ingredients used were held together reasonably well by the cement binder, with the attendant advantage of ensuring gradual release of the urea component. In this study, ingredient composition and mixing sequence were likely to have had more influence on the observed trends in block hardness and compactness than the levels of inclusion of cement, which was used as the binder. Aarts et al (1990) reported that the order of the introduction of the ingredients plays an important role in obtaining a homogenous mixture. It could be seen from Table 1 that cement inclusion level was the same (15.0 %) for seven of the nine experimental moringa multinutrient block formulae. Formulae VI and VII however had the highest percentages of wheat offals and moringa leaf powder (Table 1). Earlier reports (Ramchurn and Raggoo 2000; SMEDA 2009) indicate that wheat bran, a component of wheat offals, acts as an absorbent for the moisture contained even in molasses and gives structure to urea-molasses blocks, thus making it a logical component of multi-nutrient blocks. Mixing of cement and salt with water in the ratio of 2:1 as recommended by Aye and Adegun (2010), and preparing a separate urea solution as adopted for formulae I to VIII, in contrast to the procedure for the control procedure, led to some obvious benefits. As can be seen in Table 1, it was found to lead to a substantial reduction in the quantity of water needed for mixing of ingredients. A classical example could be seen in the comparison of the quantities of water used for the control formula and formula I with the same ingredient composition. Less water was needed for formula I relative to the control formula; 8.00 vs. 10.5 litres/10 kg of mixture (Table 1). In spite of this, there was leaking of water from the blocks from formula I when pressure was applied during moulding, as well as for almost one week during the drying period. Mixing of cement and salt with water in the ratio of 2:1 as recommended by Aye and Adegun (2010) also resulted in more homogenous mixtures, with the resultant positive effects on block hardness and compactness. Of a greater practical importance was the observation that urea was more completely dissolved alone in water than when mixed with salt, and requiring less water in the process (Table 1). A more complete dissolution of urea before incorporation into the multinutrient blocks offered a greater prospect of controlling urea intake by animals, and thus reducing the risks of urea toxicity. Additionally, the animals would be able to enjoy a regular and continuous access to urea with the attendant possibility of being able to maintain constant ammonia levels in the rumen for the growth of rumen microorganisms and high rates of fibre digestion. Sansoucy et al (1988) cautioned that the intake of urea (a component of moringa multi-nutrient blocks) must be limited to avoid toxicity problems, but sufficient to maintain ammonia levels in the rumen consistently above 200 mg N/l for growth of microorganisms and high rates of degradation of fibre. Such a regulated release of nutrients, particularly of nitrogen and carbohydrates, increases the efficiency of utilization of these nutrients (Makkar 2007). 

Nutrient and mineral characterizations of MMNBs 

The nutrient and mineral compositions of the control and selected structurally-stable multinutrient blocks are as contained in Table 4

The dry matter contents ranged from 86.0 to 88.2 % for the blocks resulting from the control formula and formula VII respectively. These dry matter levels were higher than the values reported for gliricidia-based multinutrient blocks by Aye and Adegun (2010) while they were comparable to the levels reported for urea-molasses blocks by Onwuka (1999). Such dry matter levels were regarded as quite high and indicative of reasonable extents of drying (Onwuka 1999). The crude protein contents varied between 18.4 and 22.0 %, while the predicted ME values were between 14.3 and 14.4 MJ/kg DM for multinutrient blocks from the control formula and formula VII respectively (Table 4). The crude protein levels were all higher than the minimum range of 7.00 to 8.00 % recommended for the efficient functioning of rumen microorganisms (Van Soest 1994). They also surpassed the ranges of 11.0 – 13.0 % known to be capable of supplying adequate protein for maintenance and moderate growth performances in goats (NRC 1981; Poppi and McLennan 1995). With an NPN source such as urea, ruminants would be expected to synthesize their sulphur-containing amino acids (Onwuka 1999). Laboratory analysis by Makkar and Becker (1997) showed high levels of sulphur-containing amino acids in moringa leaves. Hence, the formulated moringa multinutrient blocks are expected to provide the right types and balance of amino acids to meet the nutritional needs of ruminants. The high NFE and predicted ME values of the multinutrient blocks (Table 4) indicated high levels of energy availability to ruminants. Even though the fibre contents of the multinutrient blocks were on the low side (5.07 – 5.44 % of DM; Table 3), the fibre needs of the animals are expected to be met from their basal diets comprising of dry season feedstuffs which are usually fibrous (Dixon and Egan 1988; Leng et al 1991). The NDF and ADF contents (Table 4) were indicative of high quality feed supplement, while the hemicelluloses contents were reflective of blended forages of grasses and pure legumes (Van Saun 2007). The multinutrient blocks were observed to contain high crude ash levels, with Ca, Mg, Zn and Cu levels higher than the critical levels for goats (McDowell 1985). Other minerals such as Ca, Fe and P would also be expected to be present at nutritionally required levels since moringa leaves, one of the major components of the blocks have been reported (Makkar and Becker 1997) to contain these mineral elements. 

Cost implications of the experimental moringa multinutrient block formulae 

The unit prices in Nigerian currency (Naira) of the ingredients for making the moringa multinutrient blocks at the time of conducting the study are as contained in Table 5.

Urea was the most expensive of the ingredients at N80.0/kg while lime powder was the cheapest at N14.0/kg. The unit prices of wheat offals (N30.0/kg) and salt (N50.0/kg) were mid-way between the two limits. The unit price of cement (N78.0/kg), the binding agent in the blocks, was almost the same as that of urea.  Deliberately, no price tag was placed on the moringa leaf powder, as this is one of the subjects of an on-going multi-disciplinary research on the agronomy and economics of moringa leaf production in the derived savanna zone of Nigeria in our University, and this author is a major partner in the research team. It is however postulated that moringa leaf production cost could be minimal for ruminant livestock production through alley farming, as already observed (Olomu 1984) for gliricidia and leucaena. 

Table 6 shows the cost implications of producing the moringa multinutrient blocks. 10.0 kg mixtures of moringa multinutrient blocks were evaluated. With moulds measuring 13×13×10 cm each, 10 moringa multinutrient blocks measuring about 1 kg each, when dry, were produced from each 10.0 kg mixture. The prices per each kg of the blocks were N29.4 and N33.3 for the blocks resulting from formulae VI and VII respectively (Table 6).

Incidentally, formula VI was adjudged to have produced one of the most structurally-stable multinutrient blocks (Table 3). Comparatively, the unit price of the multinutrient blocks from the control formula was N32.3; mid-way between the prices of the structurally-stable multinutrient blocks. Using a conversion factor of N155 to one United States Dollar at the time of the study (March 2011), a metric tonne of structurally-stable moringa multinutrient blocks, comprising of 1000 units of about 1.00 kg each, would be expected to cost between N29,400 and N33,300, that is, roughly between US$190 and US$215. Wheat offals and groundnut cake, two of the most commonly-used concentrate supplements in small ruminant feeding in this environment, were sold at N30.0/kg and N96.0/kg, that is, N30, 000 and N96, 000 per metric tonne respectively at the time of the study. These two concentrate supplements are usually offered to the animals at a ratio of 50:50, thus bringing the unit price of the mixed concentrate to N63, 000/kg. With a conversion factor of N155 to a US Dollar, this translates to about US$406 per metric tonne, twice an average of about US$203 per tonne of the moringa multinutrient blocks. Labour costs were not assessed in this study. For small ruminant owners in the study area however, with flocks sizes of 1 to 6 goats and 1 to 10 sheep (Sodeinde et al 2007), and typical of the humid tropical zone of Nigeria (Matthewman 1980), the bulk of the labour requirements could be supplied by family labour. 

Conclusions

• The most desirable moringa multinutrient blocks in terms of hardness, compactness and cost were produced from a formula containing 37.0% wheat offals and 35.0% moringa leaf powder, with cement inclusion level at 15.0% as the binder. Lime powder, urea and salt inclusions were 5.00% each.
  
  
• The formulation process involved five different mixes. Wheat offals, moringa leaf powder and lime powder were measured and mixed together to form Mix 1. Urea was measured and dissolved in water to form Mix 2 while salt and cement were measured and mixed with water at the ratio of 1:2 as recommended to form Mix 3. Mix 2 was added to Mix 1 to form a paste (Mix 4), and Mix 3 was subsequently added to Mix 4. Enough water was added to form a homogenous semi-solid mixture (Mix 5) which was ready for moulding. Optimum quantity of water for the most homogenous and desirable mixture was 6.50 litres.
  
  
• Mixing of cement and salt with water in the ratio of 1:2 (w/v) led to a substantial reduction in the quantity of water needed for mixing of ingredients and more homogenous mixtures, with the resultant positive effects on block hardness and compactness.
  
  
• Urea was more completely dissolved alone in water than when mixed with salt and required less water. A more complete dissolution of urea before incorporation into the multinutrient blocks offered a greater prospect of controlling urea intake by animals, and thus reducing the risks of urea toxicity.
  
  
• During the dry season in the derived savanna zone of Nigeria, air-drying for 21 days resulted in moringa multinutrient blocks with dry matter contents regarded as quite high and indicative of reasonable extents of drying.
  
  
• The formulated moringa multinutrient blocks contained sufficient levels of energy, protein and minerals to meet the needs of ruminants.
  
  
• Formulation of moringa multinutrient blocks led to about 50.0% per unit cost of supplementation relative to a conventional mixed concentrate of equal proportions of groundnut cake and wheat offals, which could be of practical importance in commercial ruminant production.
  
  
• The potentials and prospects of the formulated moringa multinutrient blocks as dry season feed supplements in ruminant nutrition appear quite promising, with possibilities of on-farm adoption due to the simplicity in its production technology.

Acknowledgement

The pioneering efforts of Dr. O O Akinbamijo in the conceptualization and formulation of moringa multinutrient blocks while he was a Programme Leader at the International Trypanotolerance Centre (ITC), Banjul, The Gambia, are gratefully acknowledged. Dr. O O Akinbamijo is the current Head, Agriculture and Food Security Division, African Union Commission, Addis Ababa, Ethiopia.

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Received 30 December 2011; Accepted 9 February 2012; Published 4 March 2012

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