A common source of meat in West Africa is grasscutter, which is obtained from the wild. The grasscutter is a wild hystricomorphic rodent, widely distributed in most areas and constitutes an important source of animal protein (Asibey, 1974a, b; NRC, 1991). It is the second largest rodent after the porcupine. The average adult weight is 3 kg for females and 4.5 kg for males (Eben, 2004). The grasscutter has thickset body, measuring 40 to 60 cm in addition to a 20 to 25 cm tail (Fitzinger, 1995). Its furs comprise a mixture of brown-reddish and grey hairs that vary depending on its habitat (Jori and Chardonnet, 2001). Some other authors reported that the skin and hair (fur) as well as limbs and tails are easily torn out (Kingdom, 1974). This makes the animal very difficult to catch and even more difficult to handle after capture. The grasscutter is also a prominent and steady source of alternative dietary animal protein in many rural areas in Nigeria and other West African countries like Benin, Ghana, Togo, Cote D’voire (Ogunsanmi et al., 2002; Tettey et al., 2004; Ebabhamiegbebho and Ohanaka, 2012; Owen and Dike, 2012). However, the method of hunting is becoming a growing concern due to bullets containing Pb and other metals (Irschik et al., 2012; Doborowolska and Melosik, 2008; Hunt et al., 2009; ASEAN, 2012).

 

Heavy metals are ubiquitous in soil, water and air. These elements can be transferred into the food chain, thus presenting a risk for human health. Trace elements are toxic depending on dosis, and meat can be contaminated as those chemicals can be accumulated in tissues, such as Cd (Beiglbock et al., 2001) and Pb (Karita et al., 2000). Pb is a metabolic poison and a neurotoxin that binds to essential enzymes and several other cellular components and inactivates them (Cunningham and Saigo, 1997). Toxic effects of Pb are seen on haemopoietic, nervous, gastrointestinal and renal systems (Baykov et al., 1996).  In humans, high Pb concentrations can cause damage to internal organs, especially to the central nervous system (CNS), and can even reduce the ability to create new blood cells. In adults, the kidneys are the most sensitive to chronic exposure to Pb.

 

In children up to the age of 7, the nervous system is the most sensitive and such a threat is even greater in infants and small children (BfR, 2011). Humans can be exposed to Pb through foods, water, the air and dust but food is the main source of exposure (ASEAN, 2012). Cd levels have also been implicated in renal tube dysfunction (WHO, 2003). The accumulation of Cd and Pb increases with age and very high values have been registered in the muscle over surrounding the bullet pathway (Falandysz et al., 2005).

 

Determining heavy metal contamination in wild animal tissue, such as Pb and Cd can be the first step on knowing the levels of these elements, both in overall population and specific groups, such as hunters and their families. Consumption of meat from hunted wild ungulates is strictly associated with  the  issue  of  quality and hygiene assurance. The steps from hunting to market to assure meat quality are very difficult to control (Casoli et al., 2005; Coburn et al., 2005). Again, literatures on the level of these heavy metals in organs of various bush meat species particularly in Nigeria are largely unavailable. The consumers of grasscutter meat are unaware of the level of heavy metal occurrence. Moreover, heavy metal concentrations in grasscutter is a critical issue for consumer safety. The toxicity of heavy metal is one of the major environment problems and is potentially dangerous to animal and human health, because metals are able to bioaccumulate through food chain (Aycicek et al., 2008; Aschner, 2002). There is also the possibility that the heavy metal concentration levels in grasscutter varies with location/origin and thus requires investigation. Again, studies on heavy metals levels in organs of various bush meat species are scarce, particularly in Nigeria, and more research is required moreover, concentration of heavy metals in grasscutter is important for consumer safety as many grasscutter consumers are unaware of the level of heavy metal contamination in them. There is the need to improve the grasscutter meat to the status of a viable industry capable of meeting both local and foreign demands without depending largely on hunting from the wild (Adomah, 2009).

 

The objective of this study was to evaluate the levels of Pb  and Cd in muscle, liver and kidney of fresh and smoke-dried carcasses of wild and domesticated grasscutters.

Sample collection

 

Fresh and smoke-dried meats of wild grasscutter were obtained from game meat processing centres in Uwa, New Benin and Arbico markets at Benin City, Edo State, Nigeria. Moreover, fresh and smoke-dried meats of domesticated grasscutters were obtained from Makarios graduate grasscutter farmers society at Benin City, Edo State, Nigeria. The sex, age and feeding habits of grasscutter were not taken into consideration during the sampling. A total of 24 random grasscutter samples were collected between March and September 2013. A randomized complete block design was used in a 4×3×2 factorial arrangement to assess whether heavy metals varied significantly between liver, kidney and muscle of the animal. The samples were collected in separate polyethylene bags and transported to the laboratory for their analysis.

 

Sample preparation

 

All collected samples were decomposed by means of wet digestion. About 1 g of the samples (liver, kidney and muscle) was weighed into the digestion flask. Then, 5 ml of 0.1 N perchloric acid and 15 ml of 0.1 N concentrated HNO₃ in a ratio 1:3 were added and then heated in an electric plate until clarification. Following, 5 ml of 20% HCl (0.1 N) was added to the content. The content of the flask was filtered using Whatman filter NO 42 paper into a 100 ml volumetric flask and was made up to the mark with a distilled water and then stored in a plastic reagent bottle, ready for Atomic Absorption Spectroscopy (AAS) analysis. Parallelly, 5 g of the fresh and smoke-dried samples (liver, kidney and muscle) was  also  weighed in separate beakers and oven dried at 100°C to constant weight for determination of moisture content.

 

Sample analysis

 

Pb and Cd in fresh and smoke-dried liver, kidney and muscle samples were analyzed by using an atomic absorption spectrophotometer (AAS) MODEL-SOLAAR 969 UNICAM Series () at 217 nm for Pb and 228.8 nm for Cd. The allowed amounts of heavy metals (HMs) in food vary from country to country and are based on the World Health Organization (WHO) recommendations and local requirements (Oluyemi and Olabanji, 2011).

 

Statistical analysis

 

Data obtained from this study were statistically analyzed using Genstat software (2009) to establish the results. Data are shown as the mean ± standard error. Metal concentrations in fresh and smoke-dried samples were analyzed with respect to locations/origin. A statistical level of p < 0.05 was considered as significant. 

Lead (Pb)

 

The results obtained in Table 1 showed that Pb concentration was significantly higher in the liver of fresh grasscutters from Arbico market, than those levels from New Benin and Uwa markets. On the other hand, Pb concentration (mg/kg) in kidney of smoke-dried grasscutters was higher (P<0.05) at Uwa market than Pb levels at Arbico and New Benin markets (Table 2). Pb concentration was significantly higher in fresh liver, kidney and muscle than in the smoke-dried samples irrespective of the market location.

 

 

 

 

after bullet fragmentation into animal body. The levels of Pb in animals depends on various factors such as the frequency of the quantity of meat consumed, the degree of leaded-bullet fragmentation, the path that the ammunition has taken and the level of care taken to remove the flesh surrounding the wounds (Hunt et al., 2009). The results revealed that Pb levels in fresh and smoke-dried kidney, liver and meat of grasscutters were at safe levels and were of no danger to health (ANZFA, 2001). As shown in Tables 1 and 2, Pb concentrations were significantly higher in fresh tissues than in smoke-dried tissues, in agreement with the findings of Ajani et al. (2013) and Eboh et al. (2006).

 

Cadmium (Cd)

 

As shown in Table 3, Cd concentrations were significantly higher in liver, kidney and muscle of fresh grasscutters at Arbico, Uwa, New Benin and Domesticated. On the contrary, Cd concentrations were lower (P<0.05) in liver, kidney and muscle of smoke-dried grasscutters at Arbico, Uwa, New Benin and Domesticated location (Table 4). Cd concentration was the highest in fresh liver at Arbico market, whereas Cd level was the highest in smoke-dried muscle at Uwa market. In general, Cd levels in samples of kidney, liver and muscle of fresh grasscutters were significantly higher than Cd levels detected in samples of smoke-dried grasscutters.  

 

 

 

The highest Cd concentrations were observed in fresh liver (7.516 mg/kg) and smoke-dried muscle (2.723 mg/kg) from Arbico and Uwa market. Those Cd levels are above the permissible limit (0.5 mg/kg) stated in meat and liver (FAO/WHO, 2000). On the contrary, the lowest Cd concentrations were found in fresh muscle (0.186 mg/kg) and smoke-dried muscle from domesticated samples. The highest Cd levels in fresh kidney (4.045 mg/kg) and smoke-dried kidney (1.75 mg/kg) were detected in samples from Uwa market. These Cd values in kidneys are above the limit (1.0 mg/kg) accepted (FAO/WHO, 2000). Aranha et al. (1994) and Roga-Franc et al. (1996) found also Cd levels above threshold values (FAO/WHO, 2000) in liver and kidney of cattle in Poland. Doganoc (1996) found Cd levels in liver and kidney of chicken above official tolerance levels.

 

In    contrast,    Mariam    et    al.  (2004)   reported   Cd concentrations of 0.33, 0.37and 0.31 mg/kg in lean meat of beef, mutton and poultry, respectively. Previously, a study conducted at Poland by Zmudzki and Szkoda (1995) found 0.146 mg Cd/kg in liver and 0.580 mg Cd/kg in kidney of young cattle, while in older animals Cd levels were 0.204 and 0.829 mg/kg in liver and kidney, respectively. Similarly, Falandysz (1994) reported 0.10 mg Cd/kg and 0.450 mg Cd/kg in liver and kidney of cattle in northern Poland. Tahvonen and Kumpulainen (1994) reported in cattle liver, values of 0.061 mg Cd/kg from Finland, 0.070 mg Cd/kg from Sweden and 0.105 mg Cd/kg from Netherlands. Those values probably are reflecting a major environmental pollution, as also suggested by Gasparik et al. (2012), because Cd is one of the most toxic elements to humans and animals (Naja and Volesky, 2009). Cd is toxic virtually to every system in the normal body. The high levels of Cd found in both fresh and smoke-dried tissues are significantly higher than the limits set by FAO/WHO (2000). Chemically, the consumption of grasscutter meat could present a risk for human health.

 

Interactions

 

The levels of Pb and Cd found in the fresh and smoke-dried liver samples from the different locations were generally higher than the concentration  levels  of  these heavy metals in the fresh and smoke-dried kidney and muscle samples (Tables, 5, 6 and 7). However, Cd levels were lower in muscle samples than kidney and liver levels in both fresh and smoke-dried samples. This is an indication that these heavy metals accumulate more in the liver than in the kidney and muscle. However, there are a few exceptions, where the concentrations of these heavy metals are higher in the kidney and in the muscle. 

 

 

 

 

 

It is imperative to enforce actions to ensure an adequate health education to people, public health personnel and bush meat handlers through media. Grasscutter meat must be safe and suitable for human consumption, therefore all stakeholders including scientists, government, industries and consumers have a role in achieving this outcome. Sadly, West Africa has depleted stocks of wildlife, and farmers have to be financially supported by both public and private sectors toward the domestication of grasscutter. These measures could guaranty a continuous provision of meat of good quality to the growing population. In the meantime, it is highly recommended to cut off animal parts which have bullet wounds before meat processing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This study has shown that Pb levels were significantly higher in liver, kidney and muscle of fresh grasscutters than smoke-dried grasscutters. Pb was not detected in fresh and smoke-dried organs of domesticated grasscutter samples. Cd levels were highest in fresh liver and smoke-dried muscles of meat obtained from local markets even though Cd levels were lower from samples of domesticated grasscutters. Education of people and public health officials on proper bush meat handling is also highly required.

We declare that we have no conflict of interest.