Research Article
Determination of the Chemical Composition of Bush Meats Found in Nigeria
Department of General Studies, Federal College of Agriculture, Akure 340001, Ondo State, Nigeria
LiveDNA: 234.26718
Bush meats are group of animals that exist in the forest reserve. The major species in Nigeria include primates, pholidota, rodents, carnivora, hyracoidea, artiodactyla, reptiles and avian among others. The task of hunting of these animals is either simple or difficult depending on the hunter. They are either killed with traps or with guns. Human activities, like farming and felling of trees are on the increase in Nigeria and these have been affecting the population of bush meat (Abulude, 2004a).
The inadequate supply of animal protein in developing countries has been attributed to inadequate production and high cost of conventional sources of animals proteins (Poultry, goat, meat, beef, mutton and pork) hence, an average Nigeria consumes only about a quarter of his minimum daily animal protein requirement (Oke et al., 2004). To meet this problem of shortage of conventional meats, alternatives have been sourced for. To this end there has been increase in the consumption of bush meat. This increase has bridge the supply and demand protein gap (Abulude, 2004b).
Many researchers have (Abdullahi, 2000; Adeyeye, 2002, 2003; Oke et al., 2004; Omojola et al., 2004; Abulude, 2004a) reported on meat of different species of edible farm animals, especially in Nigeria, but none have worked on these bush meats reported on in this paper. The aim of this study is to examine the nutrients, minerals, anatomical weights, in vitro digestibility, organoleptic values and economic feasibility of bush meats consumed in Nigeria. It is hope that this finding will add to nutrition data.
The bush meat samples (Table 1) of ten different animals were colleted from the forest reserve of Federal College of Agriculture, Akure Campus, Nigeria, during the raining months of 2004. The rats (giant rat, Tullbergs rat, grasscutter, albino rat, tree squirrel), snakes (Cuban boa and python) and birds samples (cattle egret, pigeon bird and bat) were scarified, defeather and deskined, weighed, dissected to separate the parts and weighed in the Chemistry laboratory of Federal College of Agriculture, Akure, Nigeria.
Table 1: | Names of the meat samples used for the analysis |
Y-Yoruba name |
The meats were oven dried at 105°C between 6-10 h depending on the samples, ground in Kenwood blender, sieved (45 mm) and stored prior to analyses. Samples were analyzed for proximate composition using AOAC (1990) procedure. Carbohydrate was determined by difference. Minerals were analyzed using the Pearson (1981) methods. Digestibility, Biological Value (BV), Net Protein Utilization (NPU) and NPV were determined using the methods of Adeola (1995). Oganoleptic evaluation was carried at by a panel of 10 judges to evaluate the attractiveness, tenderness, flavor, texture, juiciness and overall acceptability on a 9-point hedonic scale (Land and Shepard, 1988). Economic feasibility was calculated for 100 g protein (NACA, 1989):
All determinations were in triplicate. Statistical evaluations were made using SPSS for windows.
The anatomical weight compositions of samples (wet weight in g) are shown in Table 2. The life weight ranged between 87.4 and 3164 in rats, 239-250 in snakes and 218-300 in birds. Most of the parts weighted in rats were consistently higher than those in snakes and birds. The life weight, intestine and length size under this study were higher than those recorded for crabs (Adeyeye, 2002). These were due to the differences in physiological compositions of the different species.
The chemical compositions of the edible portions of the bush meats selected according to their availability in the forest are shown in Table 3. Protein content of egret (76.72%), boa (63.50%), pigeon (60.63%) and bat (56.12%) were lower than those reported previously for mussel meats (78.0%; Yildiz et al., 2005) and cheliped muscle of crab (85-87%; Adeyeye, 2002), but higher then values recorded for fish (46.4%), beef (18%), lamb (16%) and pork (10%) (Abdullahi, 2000; Pearson, 1981; Guner et al., 1998). Proteins have many different biological functions: they are associated with enzymatic reactions, transport, regulation of metabolism, defence, structural elements storage. This means that a pattern can be expected, depending on different physiological activities of individuals throughout the year. Protein contents of the bush meats have been found to be of high quality similar or higher to that of meat and fish. The relative fat content varied from one meat to another but most of the species showed fat values between 2.14 and 13.28%. They belong to low fat class according to Ackmans (1989) classification, indicating the content of high ester values and good quality oils. The low contents of these samples would not allow then to contribute significantly as a source of non-visible oil to any diet in which they may be present.
Table 2: | Anatomical weight of samplesa analyzed (wet weight in g) |
a1- Giant rat, 2- Tullbergs rat, 3- Grass cutter, 4- Albino rat, 5- Squirrel, 6- Cuban boa, 7- Python, 8- Cattle egret, 9- Pigeon bird, 10- Bat |
Table 3: | Proximate composition of sample analyzed |
CC- Correlation coefficient, ±SD- Standard deviation, CV (%) - Coefficient of variation in percent |
Moisture (3.26-25.70%) and ash (0.90-24.83%) were within the ranges covered for termite (Abulude, 2004a), cricket (Abulude, 2004b) and mushrooms (Abulude 2004c). The content of moisture in all the samples would not allow any microbiological spoilage. The ash content of any sample is a measure of likely mineral content of such a sample. The low fibre content obtained in this study will help in easy digestion of the protein present in the samples. Carbohydrate content of these samples was calculated as difference between 100 and the total percentage of moisture, protein, fat and ash. There was a clear pattern in the total carbohydrate concentrations of the meats. The value was lowest in pigeon bird (0.84%) and highest in giant rat (35.08%). Carbohydrate has two major biological functions: as a long term energy store and as structural elements with lipids (Robledo et al., 1995). The implication of low carbohydrate contents of the samples is that it would be a good source of low dietary carbohydrate to the diabetic patients. The variations in proximate compositions of all the species in this study could be due to the location of catch, size, sex and types of food consumed.
Statistical results showed that correlation coefficients between the samples were highly positive in protein (0.99), ash (0.94), fat (0.84), moisture (0.49) and carbohydrate (0.94), but fibre was (-0.49). The implication of these values showed that they were highly related, but fibre did not agree with this. The mineral compositions varied with the type of meats (Table 4). The mean mineral contents (mg 100 g-1 DM) of the samples were: 6.4, 2.4, 529.8, 622.6, 477.3, 514.5, 2.5, 3.6 and 3.8 for Fe, Zn, K, Na, Ca, Mg, Cu, Mnand Cr, respectively.
Table 5: | Mineral composition of samples analyzed |
Level of significance at p = 0.05, NS-Not significance, S-Significant, ±SD- Standard Deviation, CV (%)-Coefficient of variation in percent |
The K, Na, Ca and Mg contents were significantly higher in the samples compared to micro elemental contents. In this study, the obtained Zn, Fe and Cu contents of the samples were relatively higher than 0.88, 1.56 and 0.49 mg 100 g-1, respectively, reported by Guner et al. (1997) for fishes in Turkey.
The amount of Zn obtained in this report suggest that the samples could provide a significant portion of the Nigerian Food administration for Zn. Meat is the richest source of Zn in the diet and supplies one t hird to one half of the total Zn intake of meat eaters. Consistent findings to this study with respect to Fe in wild fruits were found by Anhwange et al. (2005), but similar Fe (5.20 mg 100 g-1) and Zn (4.30 mg 100 g-1) in millipedes contents obtained by Abulude and Folorunso (2003), when compared with the current results, Abulude (2004b) reported higher Cu (10.20 mg 100 g -1) and lower Ca, Na and Mg contents. No significant differences in Pb and Cr were found in comparison with the data of Adeyeye (2000) and Hossan and Khan (2005) for prawns and shrimps, respectively.
The edible meats appeared to be good sources of K, Ma, Ca, Na and Fe. The differences in mineral contents of samples may be due to the soil, water, plant contents of their vicinities and the rate of uptake of minerals by each animal species. As current RDA of K, Ca, Na, Zn and Fe are 3750, 1200, 500, 15 and 10 (Wardlaw, 1999) a 100 g serving of the ‘bush meats would provide between 11.4-19.5, 33.9-45.8, 98-143, 6.7-28.91 and 38-119% of the adult daily requirement for the minerals.
Fe in meat is well absorbed, about 15-30%. It also enhances the absorption of iron from other sources lack of adequate iron in the diet is associated with poorer learning and decrease cognitive development (FAO/WHO, 1997). In-general, protein rich diets are rich in Zn and this is provided by animal foods (Lean meat especially beef, red meats and shellfish). Since, these ‘bush meats are rich in protein, then the availability of Zn to consumers is guaranteed. According to Wardlaw (1999) foods with highest nutrient density for Cu are animals sources, the results obtained in this study corroborate this observation. Dietary Cu is not toxic to humans because intakes are usually low and because our bodies can regulate copper storage through biliary excretion. A large amount of evidence supports the view that Cr is an essential nutrient. For instance, humans on long-term total parental nutrition containing a low amount of Cr development impaired glucose tolerance, or hyperglycemia, with glucose spilling into the urine, a resistance to insulin action. These abnormalities can be reversed by Cr supplementation (Wardlaw, 1999).
Statistical results showed significant differences in Zn and Cu contents. There were high variations in the values.
The samples were evaluated for attractiveness, tenderness, flavor, texture, juiciness and overall acceptability (Table 5). The mean score for appearance ranged from 6.50 to 7.65. Grasscutter had the highest score.
Table 5: | Organoleptic evaluation of meat samples analyzed |
a- No significance difference (p>0.05) |
Mean score for tenderness ranged from 6.99 to 7.92. Albino rat had the lowest score. Flavor scores ranged from 6.97 to 7.20, with the highest from giant rat, tullbergs rat and tree squirrel and the lowest from bat. Texture scores ranged from 6.97 to 7.15. The highest rated juiciness was recorded for grasscutter.
Color is an important indicator of the quality of fresh or cooked meat as such, the appearance of the meat (Van Oeckel et al., 1999). The panel scores for the appearance showed that the colour of meat samples were not significantly (p<0.05) affected. The scores observed in this report were in agreement with results obtained for rabbit (Omojola et al., 2004). Color of meat tends to become darker with ageand this may be of some importance with male meat which was darker than the female. Cooking is necessary to develop flavor. Mastication breaks down the fibre matrix and releases flavor-juices and the volatile aroma components into the month. The panelists assessment showed no significant (p>0.05) differences. Juiciness of meat is directly related to the intramuscular lipids and moisture content of meat (Gross et al., 1986). In combination with water, the melted lipids constitute a broth which when retained in the meat, is release upon chewing. The results of juiciness showed that panelists enjoyed the juice produced by the panelists. Tenderness is regarded as the most important sensory attribute affecting meat acceptability (Warkup et al., 1995). Meat tenderization is a multifunctional process dependent on a number of biological factors e.g., environment, sex, species and age.
The protein digestibilities of the samples examined are shown in Table 6. The values ranged from 59.96% (pigeon bird) to 68.25% (giant rat). The difference could be due to the varieties and location of catch. These values followed the trends on African Yam Bean (AYB) (Oshodi et al., 1995; Adeyeye, 1997) and tropical plant seeds (Abulude, 2005), but not in agreement with values reported for maize-tilapia flour-blendes (Fasaasi et al., 2005) and broiler meat (Oke et al., 2004). The BV ranged from a low of 47.96 in pigeon bird to a high of 54.60% in giant rat, NPU varied between 28.92 to 37.27% and NPV 6.86 to 26.12%, respectively. All these values were in close agreement with those obtained for cowpea Abulude (2004c) and Adeola (1995). The BVs were lower than egg and milk proteins (RaO et al., 1978). It has been improved in cowpea by fortification of the meal with sulphur amino-acids (Elegbede, 1998). The measure of BV and NPU of the protein is comparable with that obtained for a standard protein. BV value measures the proportion of absorbed protein from a diet that is retained while NPU measures the proportion of the consumed protein that is retained. By this standard, the most perfect protein source is egg, which is assigned the BV score of 100. Once egg white has been absorbed by the body, all of the protein it contains can be used to make new proteins with out any waste, but the score of the egg white drops slightly, to 94 in NPU. The average NPU scores for plant-derived proteins are lower than (55) those for animal-derived proteins (75) (Nieman et al., 1992). Cooking methods, accompanying nutrients and complementary protein sources can all improve the NPU of a meal. It is known that supplementation of legumes with cysteine and methioninne dramatically improved BV and NPU of cowpea (Elegbede, 1998). It is therefore suggested that supplementation of these meat samples with sources of methionine and cysteine or other amino acids would improve both their BV and NPU and enhance their overall nutritive values.
Table 6: | Digestibility of meat samples analyzed |
BV- Biological value, NPU- Net protein utilization, NPV- Net protein value, ±SD- Standard deviation, CV (%)- Coefficient of variation in percent |
Table 7: | Economic Feasibility of meat samples analyzed |
# - Naira (Nigerian currency) |
The significantly highest price of 100 g protein (#, Naira) as found in grass cutter (3524.2) and the significantly lowest was in bat (115.8) belonging to mammal and bird, respectively (Table 7). In the present study, meat samples of mammals had high price values. This may be due to the fact that they are not common in the foods sold at cafeterias and resturants.
Economically, cuban boa, cattle egret, pigeon bird and bat were found to be the cheapest sources of protein. In Nigeria, the conventional sources of meat proteins are mainly from livestock production, due to high cost of production, alternative meats were sourced for hence leading to back yard rearing of rats like rabbits, albino rats, grass cutters just to mention a few. These animals are reared because of their cheap feeding, high birth rate and palatability.
The present results showed that the bush meats samples have high protein values and valuable minerals. Their digestibilities were high. Economically, it was observed that the meat samples that produced the cheapest source of protein were cuban boa, cattle egret and bat, but if the rats are domesticated they would be excellent and cheaper sources of animal protein. Their nutritional qualities compared to the conventional meats-pork, beef, mutton and poultry. It is therefore advisable for people to take the advantages of their nutritional benefits.
The author is grateful to Messers Onuoha. Imoh Williams, Pius Adeluka; Ayorinde Oni, Gabriel Akinleye, I. Ajao and Miss Patricia Akinbuli. All of Federal College of Agriculture, Akure, Nigeria for the provision of cattle egret, tullbergs rat, grass cutter, cuban boa, giant rat, albino rat and pigeon bird, respectively and to Messers Oguntokun M.O and Oseke M.O for the determination of proximate and mineral compositions, respectively.