Proximate composition of the leaves of Bambusa ventricosa , Oxytenanthera abyssinica and two varieties of Bambusa vulgaris

Food selection by herbivores depends on the dietary composition of plant parts. However, the nutritional properties of tropical bamboo leaves, which could be a viable supplement of traditional fodder are hardly examined. Proximate composition of Bambusa ventricosa McClure, Oxytenanthera abyssinica (A. Rich.) Munro and two varieties of Bambusa vulgaris (B. vulgaris Schrad. ex J. C. Wendl. var. vulgaris Hort. and B. vulgaris Schrad. ex J. C. Wendl. var. vittata Rivière) leaves were determined. B. ventricosa proximately comprised 10.34% moisture, 1.38% crude fat, 11.56% ash, 19.02% crude protein, 27.20% crude fibre and 30.40% carbohydrate. O. abyssinica leaves contained 10.34% moisture, 1.38% crude fat, 12.56% ash, 19.39% crude protein, 26.78% crude fibre and 29.55% carbohydrate. B. vulgaris vulgaris had 10.34% moisture, 1.49% crude fat, 12.53% ash, 18.39% crude protein, 25.88% crude fibre and 31.38% carbohydrate, while B. vulgaris vittata contained 10.71% moisture, 1.58% crude fat, 8.73% ash, 18.75% crude protein, 33.19% crude fibre and 27.04% carbohydrate. Moisture content of bamboos is important, as it determines their susceptibility to microbial infection. The low moisture of the bamboo leaves is an index of the great shelf-life of their meal. These leaves are also a good aminoacid source (especially for O. abyssinica), while their carbohydrate and great fibre contents (as in B. vulgaris varieties) are a rich roughage supply. They are highly nutritious and could be used as alternative local feed resources suitably as fodder for livestock or wildlife and alongside other feed sources containing proteins and minerals to ensure food security in the tropics.


INTRODUCTION
Bamboo (Family: Poaceae) is a grass with a woody culm (stem), which is used often in construction much like conventional wood (Zehui, 2007;Anonymous, 2011a).At least, one third of the human race uses bamboo in one way or another (National Geographic Society, 1980;INBAR, 1997).In East Asia in particular, ITTO (2009) reported that man cannot survive without bamboo, while the use of this plant is limited in the tropics.However, effective utilization for the whole plant would absolutely make it a suitable replacement for the traditional tropical timber species.Bamboo has a wide distribution in the tropics and sub-tropics ranging from latitude 46° N to 47°S, and at elevations as high as 4,000 metres such as in the Himalayas and several parts of China to sea level in different areas (National Geographic Society, 1980;Liese, 1985).Four main species of bamboo have been recorded with several varieties in Ghana: Bambusa ventricosa McClure, Oxytenanthera abyssinica (A.Rich.)Munro and two varieties of Bambusa vulgaris (that is, B. vulgaris Schrad.ex J. C. Wendl. var. vulgaris Hort. and B. vulgaris Schrad. ex J. C. Wendl. var. vittata Rivière).The most widespread among these species, however, is B. vulgaris, which constitutes about 95% of the total bamboo resources.Two distinct varieties (that is, B vulgaris var.vulgaris and B vulgaris var.vittata) grow in Ghana and are regarded as native.The green variety (that is, B vulgaris var.vulgaris) is more common than the yellow (that is, B vulgaris var.vittata), which is often cultivated (Ebanyenle et al., 2005).This grass has many applications such as the production of panels, lumber, veneer, plywood, pulp and paper, charcoal, vinegar and flooring from their culms (Zehui, 2007).Bamboo is a major Non-Timber Forest Product (NTFP) whose exploitation should provide local people with sufficient food and fodder for their livestock and contribute to the development of herbal medicine as well as generate income (ITTO, 2009).Herbivores feed on plants based on their composition.
These include protein, phosphorus, and carotene (vitamin A), which are the principal components that may be limiting in plants on rangelands (Ruyle, 1993).These constituents occur in various above-ground parts of grasses such as the leaves.However, the inherent content of leaves is affected by leaf age, plant age and the position of the leaf (Harding et al., 1962;Marchal, 1984).Although, there is no documented evidence of the use of bamboo leaves as fodder in several developing countries, Farrelly (1984) reported that the giant panda feeds exclusively on bamboos, that is, their leaves, culms and roots.The leaves of B. vulgaris are very rich in nitrogenous material; they are a valuable feed, which cattle and horses eat with zest, while B. vulgaris and B. ventricosa are excellent sources of vitamin A. After harvesting culms of woody bamboo plants, livestock feed on their leaves as fodder, which is a common practice in China and Jamaica (Farrelly, 1984).However, this is hardly the situation in the tropical countries due to the paucity of information on their nutritional constituents (Ebanyenle et al., 2005).This research sought to provide compositional information on African bamboo leaves, which could be employed for livestock production in developing countries where animal food security is a problem.Thus, the study examined the proximate composition of four tropical bamboos so as to establish their nutritional suitability as fodder or feed for livestock or other animals.This can serve as a significant means of converting otherwise unusable parts of tropical bamboos into high quality animal protein.

Collection of bamboo leaves
Leaves of B. ventricosa, B. vulgaris and O. abyssinica were collected from the bambusatum of the Forestry Research Institute of Ghana (FORIG) at the Bobiri Forest Reserve near Kumasi, in the Ashanti Region, which occupies about 10.2% of the total land area of Ghana.The area lies within a Moist Semi-Deciduous Forest type, while the soil is the Forest Ochrosol type.Rainfall is between 1250 to 1500 mm per annum with a bimodal pattern -a major in May-June and the minor around September-October (Hall and Swaine, 1981).Green healthy bamboo leaves were plucked at random from 1.5 m above ground-level from three-and-a-half year old stands.Plucking was done just before the end of April at a time nonstructural carbohydrate content (TNC) levels were expected to be critically low (Wilson and Mannetje, 1978).

Proximate analysis of bamboo leaves
Leaf samples from each bamboo variety were individually subjected to proximate analysis using techniques prescribed by Association of Official Analytical Chemist [AOAC] (1990).This constitutes the class of food present in samples such as carbohydrate, protein, fat, fibre, ash and moisture contents (Iniaghe et al., 2009).Crude protein was determined using the micro-Kjedahl method (Shaw, 2006).Total ash was analyzed by incineration, crude fibre by incineration after acid and base digestion and crude fat by Soxhlet extraction.Moisture content was determined by oven-dry method and carbohydrates by difference (Pearson, 1976).There were triplicates for each analysis and their mean values and standard deviations determined.Composition of the bamboo leaves was compared with those established for three species of the high quality fodder, Acalypha (Family: Euphorbiaceae) determined by Iniaghe et al. (2009), elephant grass, Pennisetum purpureum (Okaraonye and Ikewuchi, 2009), cassava leaves (Manihot utilisima) and Talinum triangulare (Akindahunsi and Salawu, 2005;Iniaghe et al., 2009), Occimum graticimum and Hibiscus esculentus (Akindahunsi and Salawu, 2005) under similar conditions using the same protocols.

Determination of energy content of bamboo leaves
The total energy contents (that is, calorific values) of the bamboo leaves were determined based on the Atwater factor (FAO, 2006).These calorific values were compared with those determined by the bomb calorimeter.The amount of oxygen involved in the combustion of dry powdered leaf sample of each bamboo variety (1 g) was compared directly with the heat of combustion as determined in the calorimetric bomb (Mullan, 2006).Energy contents of the bamboo leaves were also compared with those of Acalypha (Iniaghe et al., 2009) and P. purpureum (Okaraonye and Ikewuchi, 2009), which were analyzed using the same standards.

Statistical analysis
Data obtained were subjected to Analysis of Variance (ANOVA) with values for p < 0.05 considered significantly different.Least Significant Difference (LSD) was used to identify significant differences between treatment means.

Proximate composition
Proximate compositions of the sampled bamboo leaves are represented in Table 1.Except for the yellow variety of B. vulgaris (that is, B. vulgaris var.vittata), the most prominent constituent in all the varieties was carbohydrate, which ranged from 27.04% (for B. vulgaris  vittata) to.31.38% (for B. vulgaris vulgaris).The moisture and the total ash contents were very low in all the varieties.The lipid content of the leaves was extremely low (between 1.38% in O. abyssinica and 1.58% in B vulgaris var.vittata).From the proximate analysis, the major components of bamboo leaves are: carbohydrates, crude fibre and protein; the three together constitute over 75% of the leaves.The leaves of B. vulgaris var.vittata have comparatively high crude fibre content (33.19%) and very low total ash content (8.73%).O. abyssinica leaves have the lowest crude fat content (1.38%) but the highest ash (12.56%) and protein (19.39%) contents.
Table 1 shows that no significant differences (p < 0.05) exist between the values obtained for any one constituent among the bamboo varieties.

Food energy values
Calorific values for the leaves of the bamboo varieties, using a conversion factor of 4.184 (Anonymous, 2011b) Okaraonye and Ikewuchi (2009) for the much grazed elephant grass, P. purpureum (that is, 30.91%).Thus, like the much preferred fodder plant (P.purpureum) by livestock and wildlife, these bamboo leaves are a good source of carbohydrates or energy.The relatively high crude fibre content of these bamboo leaves (that is, 25.88 to 33.19%) suggests that animals will prefer them less to alternatives that have lower crude fibre such as P. purpureum, which has 9.09% (Okaraonye and Ikewuchi, 2009).These could explain why bamboo leaves are reported by Farrelly (1984) to impart superior physical tone and stamina to horses since fibre speeds up the process of digestion by improving peristalsis.According to the investigations made by Saldanha (1995) and UICC/WHO (2005), the high crude fibre content also means bamboo leaves of these varieties could be instrumental in colon cancer prevention in humans and in the treatment of obesity, diabetes and gastrointestinal disorders.The leaves of the bamboos showed crude protein content (18.39 to 19.39%) to be lower than that recorded for cassava (M.utilisima) leaves, which contain 24.88%, and 31.00% for T. triangulare (Akindahunsi and Salawu, 2005;Iniaghe et al., 2009).However, the value is greater than those recorded for the three species of Acalypha (that is, 13.78, 16.19 and 18.15% for A. hispida, A. racemosa and A. manginata, respectively).Elephant grass and bamboo belong to the same family (Poaceae), yet the former has greater crude protein content (27.00%) than that of any of the bamboo varieties analysed.This makes bamboo leaves a less nutritious feed source for high-protein demanding animals such as nursing cows and convalescents.Elephant grass will be a better alternative except that, unlike bamboo leaves, it contains high crude fat content (14.82%), which such animals may find difficult to metabolise (Chaney, 2006).Moreover, the crude fat contents of the bamboo leaves, which range from 1.38 to 1.58%, are lower than those recorded for the three Acalypha species (6.15, 6.30 and 6.60% for A. hispida, A. racemosa and A. manginata, respectively), Baseila alba (8.71%), Amaranthus hybridus (4.80%) and 5.90% for T. triangulare (Akindahunsi and Salawu, 2005;Iniaghe et al., 2009).The little amount of crude fat for the bamboo leaves as well as their low moisture content would make bamboo leaves decayresistant, as these would limit the growth of decay microorganisms and prolong their storage lives (Adeyeye and Ayejuyo, 1994).Thus, the efficacy or bioactivity of extracts from the bamboo leaves as a potential organic preservative in preventing bio-deterioration of on-farm wooden structures and other natural resources, where toxic conventional inorganic preservatives may be undesirable, need investigating.The ash content of the bamboo leaves was great (ranging from 8.73% for B. vulgaris vittata to 12.56% for O. abyssinica), which suggests their possession of a large deposit of mineral elements (Antia et al., 2006).
Although their ash contents compare with those of several vegetables including O. graticimum and H. esculentus (that is, 8.00%) reported by Akindahunsi and Salawu (2005), they are by far less than those recorded for the leafy vegetable T. triangulare (20.05%), which is often used as a palatability improver in pasture as well as the valuable forage, P. purpureum (18.18%).However, they are greater than 3.17% recorded for chestnuts (Castenea spp.) (Amoo et al., 2008).Geography affects the bio-chemistry of organisms, particularly plants.The ash content of plants is directly related to the mineral composition of the soil, that is, their growth sites.This situation is evidenced by the fact that previous figures for various bamboo species collected from different parts of the world by FAO (2006) ranged from 3.3% especially for Arundinaria cannaviera collected in Brazil to 16.9% for B. vulgaris collected in Jamaica (INBAR, 2010).Thus, the ash contents for these tropical varieties (8.73 to 12.56%) appear unique.Even though the bamboo leaves contain low crude fat, their protein and high carbohydrate values compensate, to an extent, for their relatively high energy values.Chestnut and sponge gourd (Luffa aegyptica) have energy values of 542.29 kcal and 451.97 kcal, respectively (Amoo et al., 2008), while Okaraonye and Ikewuchi (2009) recorded 313.45kcal for P. purpureum.
However, the average energy value for the bamboo leaves under investigation is 207.26 kcal, using a conversion factor of 4.184 (Anonymous, 2011b).Based on high carbohydrate and protein contents, coupled with the calorific values, bamboo leaves are suitable for the feeding of animals.Thus, they could be fed to livestock as fodder just like the highly palatable and most valuable forage, P. purpureum.However, these leaves alone should be fed to animals preferably in large quantities (the abundance of B. vulgaris especially will support this) to compensate for its deficiencies, or as a therapy for obesity, diabetes, gastrointestinal disorders, and prevention of colon cancer or in combination with other feed sources containing higher levels of protein and total ash (minerals).This would promote the efficient and sustainable whole utilization of the tropical bamboos, which would otherwise pose a major waste disposal problem.Utilization of the leaves would contribute to broaden the raw material base for non-timber wood products usually employed as a fodder source for farm animals in developing countries, especially in areas where it is increasingly difficult to maintain food security.

Conclusion
The proximate composition of the four important tropical bamboos reveals that their leaves are carbohydrate-rich when compared with components of the leaves from several vegetables, which are usually employed as forage or palatability improvers in pasture.Their low moisture content is an index of their great permanence due to less microbial susceptibility and long shelf-life of their meal.Their average protein content is a source of amino-acid, while their great fibre, coupled with great carbohydrate contents, would serve as a rich roughage supply.Lack of fodder in developing countries, for the greater parts of the year (especially at the long dry periods), poses a grave threat to food security, as these do not make animals in these localities productive.Thus, the feeding of livestock and other animals using the nutritious leaves of these bamboos as fodder is viable depending on their nourishment or therapeutic needs.

Figure 1 .
Figure 1.Food energy values for dry powdered leaf samples for four tropical bamboo varieties; NB: Conversion factor for the energy values (kcal) = 4.184 (Anonymous, 2011b).

Table 1 .
Proximate composition of dry powdered leaf samples for four tropical bamboo varieties. *Nutrient