Proximate composition and mineral profile of elephants forages in the Savannah ecological zone of Ghana

ABSTRACT

This study evaluated the proximate and mineral composition of various parts of Balanites aegyptiaca, Mitragyna inermis, Cassia sieberiena, Kigelia africana, Detarium microcarpum, Terminalia laxiflora, Ficus platyphylla and Climber plant (Liana) as feeds of elephants in the savannah ecological zone of Ghana. The proximate composition was carried out using the methods of the Association of official analytical chemists (AOAC) and the mineral profiles were determined by atomic absorption and flame photometric methods. The highest content of Crude Protein, Crude Fibre, Ash, Moisture and Nitrogen free extract were 12.0% ± 0.01, 15.3% ± 0.01, 14.6% ± 0.0, 7.5% ± 0.01, 76.6% ± 0.01 for Ficus platyphylla, Tamarindus indica, Balanites aegyptiaca and Detarium microcarpum, respectively. The mineral profiling also found appreciable levels of Ca, Mg, P, K, Na, Zn, Cu, Fe, Se and Mn at concentrations (mg/kg) of 4.6 ± 0.00, 0.4 ± 0.01, 0.4 ± 0.01, 5.1 ± 0.01, 0.11 ± 0.01, 1.07 ± 0.008, 0.25 ± 0.005, 0.063 ± 0.0005, 37.48 ± 0.001 for Ficus platyphylla bark, Liana, Terminalia laxiflora bark and leaves, Mitragyna inermis bark, Terminalia laxiflora leaves and Mitragyna inermis leaves, respectively. Presentation of the presence of these important nutrients would be a guide to zoo managers and wildlife practitioners on the best quality of feeds to select for wild elephants.

KEYWORDS:

• Elephants
• proximate
• Loxodonta africana
• Savannah
• ecological zone

Introduction

Estimating nutrient and mineral requirements for wildlife is a necessary tool in managing and controlling the nutritional needs of zoos and other wildlife facilities. The daily intake of food by African elephants is purged at 1.25% of body weight. It has been reported that in the dry season, females consumed 3% leaves and 14% bark, whereas males consumed 1% leaves and 6% bark and additional twigs (Greyling 2004).

The feeding habit of elephants shows a great variance with respect to the seasons, availability of natural water and traditional movements (Chakuya and Moyo 2016). African elephants are described as generalist feeders as they feed on trees, shrubs, grasses, herbs and fruits depending on availability. Some negative effects of elephants feeding activities on other herbivores are mainly due to pushing over, uprooting and snapping of trees. Thus, elephant feeding is associated with the destruction of trees which in the 1970s was described as the ‘elephant problem’ among most zoos and parks.

Foraging behaviour is a demonstration of the food choice of elephants but is insufficient to quantify the proximate composition and mineral profile in these herbages (Appiah et al. 2018). Chemical analysis of the herbages is required to determine the proximate composition and mineral profile of herbages (Chakuya and Moyo 2016). This will provide information on the proximate composition and mineral profile of herbage consumed by elephants. Browsing enhances the mineral composition of elephant feeds and other biological functional elements (Holdo 2003). Biological functional elements such as calcium, phosphorus, magnesium, potassium and sodium are mostly higher in younger herbages than older plants. It has been estimated that folia calcium, phosphorus, magnesium and potassium accumulate more in mature leaves in the dry season than experienced in the wet season (McNaughton et al. 2006). Tree barks are rich in calcium making it a preferred feed by elephants for the healthy growth of skeleton and stronger tusks in male elephants (Farhath et al., 2001). Thus, bark from woody plants is often ripped off for feeding purposes. Research has also established that herbivores prefer herbage with higher nutritional content compared to herbage with low nutritional value (Debela et al. 2015). This might have influenced the selection of the identified herbages in the current study.

The amount and type of herbage that an herbivore will remove from a plant during foraging will be influenced by the need to meet daily metabolic requirements as determined by body size (Owen-Smith 1988). The natural diet of an elephant is characterized by high fibre content (30%–50%) and a low-to-moderate protein content (8%–12%). Elephants as browsers, pluck forage broken off the plant or the entire plant uprooted or strip off branches. They also run branch tips between their teeth to strip off the bark, discarding the interior wood (Chafota 2007).

Elephants are found most often in savannas, grasslands and forests and occupy a wide range of habitats, including deserts, swamps and highlands in tropical and subtropical regions of Africa and Asia.

The habitat of African elephants includes tropical grassland and forests, woodlands and savannas. The habitat of African elephants in the Savannah Ecological Zone is characterized by broken trees and woody plant structures as a result of the activities of these elephants. Several studies have suggested that nutrition and mineral consumption in particular, may be important in affecting elephant population densities (Shoroff et al. 2000). Sometimes, elephants could migrate many miles (Farhath et al., 2001) in search of food. However, a comprehensive look at the nutritional content of elephant diets and the identification of potentially limiting nutrients is largely lacking (Rode et al. 2006).

This research aims at assessing the proximate composition and mineral profile of feed of African elephants in the Savannah Ecological Zone of Ghana. The findings will also compare the proximate composition and mineral profile of the herbages of elephants to help select those herbages that contain mineral contents within the daily recommended levels necessary for elephants’ health. The results would provide mahouts and other managers of captive elephants the knowledge for careful selection of plant species to maintain for nutrition and health of elephants.

Materials and methods

Study area

The study was conducted in the Larabanga enclave within the Savannah Ecological Zone of Ghana. The study area comprised the central town of Larabanga, a village in the West Gonja district which is a fringe community to the Mole National Park. It lies on latitude 9°12¹56.16 to the north and longitude −1°51¹31.18 to the East. Larabanga is known, among other things for its patterned vernacular architecture and also as the entrance to the Mole National Park. Mole is home to the elephants (and other game). So the elephants feed within and around the reserve, including the fringe community. A descriptive map of the study area is shown in Figure 1. The current study was carried out between January 2020 and August 2021.

Figure 1. A map showing the districts and landmarks within the savannah ecological zone of the study area (Google map data, 2022).

Identification and sampling of elephants’ feeds

The plants and plant parts eaten by African elephants within the Larabanga enclave of the Savannah Ecological Zone were identified through questionnaires and a community member’s guide. The rationale for the issuance of the questionnaire was to obtain information on the feed types consumed by elephants, either plants or trees, grasses or whether elephants consume a mixture of the plants and grasses in the Savannah ecological zone of Ghana. A total of fifty (50) respondents were interviewed which comprised staff of the Mole National Park and other fringe community members. This was also confirmed by close observation of the feeding habits of the elephants in terms of the frequency of foraging on specific plants and plant parts. The plants were later identified by a Botanist at the University of Energy and Natural Resources, Ghana and grouped according to the frequency of preference by the elephants. The plants identified are Cassia sieberiena, Kigelia africana, Mitragyna inermis, Tamarindus indica, Terminalia laxiflora, Detarium microcarpum, Ficus platyphylla and Balanites aegyptiaca. All the plants used in the study were identified in the field. The parts of these plants eaten by elephants were sampled and processed for laboratory analysis (AOAC, 2003; Baraem 2017).

Laboratory analysis

The plants or plant parts eaten by the elephants were harvested into a zip-lock bag at the field and transported to the laboratory. The samples were then thoroughly washed under running water and air-dried at room temperature. The dried samples were pulverized and stored in glass containers and put in a fridge until used. The proximate composition (Moisture, crude fibre, crude fats, Nitrogen free extract and Ash) of the selected elephant feed was determined by employing the methods of AOAC, (2003).

The mineral profiles (Ca, Na, K, Mn, Mg, Se, Fe, Cu, P and Zn) of the selected elephant feeds were conducted according to the methods of Baraem (2017).

Results

Discussion

Analysis of the forage selection by African elephants (Loxodonta Africana) in the Savannah Ecological Zone indicates the browsing of a large variety of plant species in the study area. During the onset of the dry season, most grasses and shrubs were removed by bush fires leaving trees and shrubs and fresh grasses only at watersheds. The selection of feeds for the current research was limited to the foliage of trees and shrubs. However, the selection of feeds is supported by the findings of Sukumar (1990), which established that elephants prefer plants to grasses in the late wet season to the dry season due to the palatability and nutrient concentration of plants. Plants identified were Cassia sieberiena, Kigelia africana, Detarium microcarpum, Ficus platyphylla, Tamarindus indica, Mitragyna inermis, Balanites aegyptiaca and Terminalia laxiflora. Research shows that nutrient concentration tends to decline in the dry season for the grasses but is appreciably higher in plants. As such, the selected plant and parts in the study conformed with the observed forage selection of elephants at the Luangwa Valley, Zambia. It was observed that elephants consumed more bark, leaves and roots in the dry season (Lewis, 1986). Also, research conducted at the Rajaji National Park revealed a preference for plant species compared to grass species, shrub and climber species (Williams 2002), similar to that reported at the Manas National Park and also that at the Shangyong National Natural Reserve, Xishuangbanna, China (Chen et al. 2006).

The chemical analysis of selected herbages revealed the levels of proximate and mineral compositions, as shown in Tables 1–3.

Table 1. Proximate content (Mean ± SD) of selected feeds of African elephants (calculated as a percentage of Dry weight) as mature plants and shrubs.

Plant name	Part (s) used	Sample code	Moisture	Ash	Crude protein	Total fats	Crude fibre	Nitrogen free extract
			Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD
Cassia sieberiena	Root	CSR	7.6 ± 0.02	9.6 ± 0.01	7.5 ± 0.01	1.0 ± 0.05	2.6 ± 0.00	71.6 ± 0.01
Kigelia africana	Leaves	KAL	11.4 ± 0.02	14.2 ± 0.01	10.6 ± 0.01	2.5 ± 0.02	1.2 ± 0.01	60.0 ± 0.01
	Stembark	KAS	8.2 ± 0.01	12.2 ± 0.01	3.5 ± 0.01	1.0 ± 0.01	1.0 ± 0.00	74.1 ± 0.09
Detarium microcarpum	Fruits	DMF	11.9 ± 0.02	3.8 ± 0.01	3.5 ± 0.01	3.5 ± 0.02	0.5 ± 0.01	76.6 ± 0.01
	Leaves	DML	9.2 ± 0.01	3.8 ± 0.00	3.1 ± 0.00	7.5 ± 0.01	0.6 ± 0.01	75.9 ± 0.01
Ficus platyphylla	Stembark	FPS	7.4 ± 0.01	14.1 ± 0.01	12.0 ± 0.01	4.0 ± 0.00	3.2 ± 0.01	9.3 ± 0.01
	Leaves	FPL	9.2 ± 0.01	14.5 ± 0.01	11.1 ± 0.01	2.0 ± 0.01	1.5 ± 0.00	61.6 ± 0.01
Climber	Whole plant	CWP	9.2 ± 0.01	9.2 ± 0.01	3.5 ± 0.00	1.5 ± 0.01	4.1 ± 0.01	72.4 ± 0.01
Tamarindus indica	Fruits	TIF	9.2 ± 0.01	4.5 ± 0.01	8.0 ± 0.01	1.0 ± 0.00	2.6 ± 0.01	74.7 ± 0.01
	Stembark	TIS	5.4 ± 0.01	15.3 ± 0.01	3.5 ± 0.01	1.0 ± 0.01	12.8 ± 0.01	62.0 ± 0.01
Mitragyna inermis	Leaves	MIL	8.0 ± 0.00	5.1 ± 0.01	11.1 ± 0.01	4.0 ± 0.00	1.0 ± 0.01	70.7 ± 0.01
	Stembark	MIS	9.8 ± 0.01	12.7 ± 0.01	5.3 ± 0.00	1.5 ± 0.01	3.7 ± 0.01	67.0 ± 0.01
Balanites aegyptiaca	Fruits	BAF	14.6 ± 0.01	4.2 ± 0.01	4.9 ± 0.01	2.0 ± 0.00	2.2 ± 0.01	72.0 ± 0.01
Terminalia laxiflora	Stembark	TLS	9.2 ± 0.00	14.7 ± 0.01	4.0 ± 0.02	2.0 ± 0.01	2.1 ± 0.01	68.0 ± 0.01
	Root	TLR	10.0 ± 0.00	11.8 ± 0.01	4.4 ± 0.01	1.5 ± 0.00	1.5 ± 0.01	70.7 ± 0.01
	Leaves	TLL	8.6 ± 0.01	7.7 ± 0.01	9.3 ± 0.01	4.5 ± 0.00	0.5 ± 0.01	69.3 ± 0.01

Table 2. Levels (Mean ± SD) of analyzed macro-minerals in selected feeds of African elephants.

Name plant	Part used	Sample code	Ca (mg/kg)	P (mg/kg)	Mg (mg/kg)	Na(mg/kg)	K (mg/kg)
			Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD
Cassia sieberiena	Root	CSR	1.1 ± 0.00	0.1 ± 0.01	0.1 ± 0.00	0.06 ± 0.00	2.4 ± 0.00
Kigelia africana	Leaves	KAL	2.0 ± 0.01	0.5 ± 0.01	0.2 ± 0.01	0.07 ± 0.01	3.9 ± 0.01
	Stem bark	KAS	1.1 ± 0.00	0.1 ± 0.01	0.1 ± 0.00	0.04 ± 0.00	1.3 ± 0.00
Detarium microcarpum	Fruits	DMF	0.2 ± 0.01	0.0 ± 0.00	0.1 ± 0.01	0.07 ± 0.01	4.2 ± 0.00
	Leaves	DML	0.3 ± 0.00	0.3 ± 0.01	0.3 ± 0.00	0.07 ± 0.00	3.4 ± 0.00
Ficus platyphylla	Stembark	FPS	4.6 ± 0.00	0.1 ± 0.00	0.2 ± 0.00	0.07 ± 0.01	3.6 ± 0.01
	Leaves	FPL	2.5 ± 0.01	0.2 ± 0.00	0.2 ± 0.01	0.07 ± 0.01	3.8 ± 0.01
Climber plant	Whole plant	CWP	0.9 ± 0.01	0.4 ± 0.01	0.4 ± 0.01	0.11 ± 0.01	4.8 ± 0.00
Tamarindus indica	Fruits	TIF	0.5 ± 0.00	0.2 ± 0.01	0.1 ± 0.01	0.08 ± 0.00	3.5 ± 0.00
	Stembark	TIS	4.4 ± 0.01	0.1 ± 0.00	0.3 ± 0.00	0.07 ± 0.01	1.3 ± 0.01
Mitragyna inermis	Leaves	MIL	0.9 ± 0.01	0.4 ± 0.01	0.3 ± 0.01	0.08 ± 0.00	3.5 ± 0.01
	Stembark	MIS	2.5 ± 0.01	0.2 ± 0.01	0.4 ± 0.01	0.11 ± 0.01	5.1 ± 0.01
Balanites aegyptiaca	Fruits	BAF	0.4 ± 0.01	0.2 ± 0.01	0.1 ± 0.01	0.07 ± 0.01	4.2 ± 0.00
Terminalia laxiflora	Stembark	TLS	4.4 ± 0.00	0.4 ± 0.01	0.2 ± 0.00	0.07 ± 0.00	1.9 ± 0.01
	Root	TLR	3.0 ± 0.00	0.3 ± 0.00	0.1 ± 0.01	0.07 ± 0.00	1.9 ± 0.00
	Leaves	TLL	1.4 ± 0.01	0.4 ± 0.01	0.2 ± 0.01	0.07 ± 0.01	3.0 ± 0.01

Table 3. Levels (Mean ± SD) of analyzed micro-minerals of selected feeds of African elephants.

Name of plant	Part(s) used	Sample code	Fe (mg/kg)	Zn (mg/kg)	Cu (mg/kg)	Se (mg/kg)	Mn (mg/kg)
			Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD
Cassia sieberiena	Root	CSR	0.002 ± 0.0008	0.73 ± 0.008	0.07 ± 0.008	0.0030 ± 0.0008	3.52 ± 0.042
Kigelia africana	Leaves	KAL	0.006 ± 0.0005	0.56 ± 0.008	0.12 ± 0.008	0.0050 ± 0.0008	1.24 ± 0.005
	Stembark	KAS	0.002 ± 0.0005	0.39 ± 0.008	0.07 ± 0.009	0.0030 ± 0.0008	0.64 ± 0.009
Detarium microcarpum	Fruits	DMF	0.002 ± 0.0005	0.56 ± 0.005	0.05 ± 0.005	0.0030 ± 0.0008	0.77 ± 0.008
	Leaves	DML	0.003 ± 0.0005	0.61 ± 0.008	0.12 ± 0.008	0.0027 ± 0.0005	4.01 ± 0.008
Ficus platyphylla	Stembark	FPS	0.003 ± 0.0005	1.07 ± 0.008	0.11 ± 0.008	0.0037 ± 0.0000	0.36 ± 0.005
	Leaves	FPL	0.004 ± 0.0008	0.77 ± 0.008	0.13 ± 0.005	0.0030 ± 0.0000	0.64 ± 0.005
Climber plant	Whole plant	CWP	0.003 ± 0.0005	0.52 ± 0.005	0.11 ± 0.008	0.0027 ± 0.0005	0.42 ± 0.005
Tamarindus indica	Fruits	TIF	0.002 ± 0.0005	0.82 ± 0.008	0.15 ± 0.005	0.0020 ± 0.0008	0.87 ± 0.008
	Stembark	TIS	0.002 ± 0.0005	0.37 ± 0.009	0.20 ± 0.005	0.0033 ± 0.0005	0.66 ± 0.008
Mitragyna inermis	Leaves	MIL	0.007 ± 0.0005	0.53 ± 0.008	0.25 ± 0.005	0.0057 ± 0.0009	37.48 ± 0.008
	Stembark	MIS	0.004 ± 0.0005	0.41 ± 0.008	0.14 ± 0.005	0.0033 ± 0.0005	19.47 ± 0.008
Balanites aegyptiaca	Fruits	BAF	0.003 ± 0.0008	0.36 ± 0.008	0.06 ± 0.008	0.0023 ± 0.0005	0.48 ± 0.008
Terminalia laxiflora	Stembark	TLS	0.003 ± 0.0005	0.87 ± 0.008	0.19 ± 0.005	0.0030 ± 0.0000	3.63 ± 0.047
	Root	TLR	0.003 ± 0.000	0.48 ± 0.008	0.12 ± 0.008	0.0033 ± 0.0005	0.84 ± 0.008
	Leaves	TLL	0.063 ± 0.0005	0.90 ± 0.005	0.12 ± 0.008	0.0643 ± 0.0005	25.37 ± 0.047

The preference of the selected plant parts by elephants within the Savannah Ecological Zone conforms with the observed forage selection of elephants at the Luangwa Valley, Zambia, it was observed that elephants consumed more stembark, leaves and roots in the dry season and this might be in response to the daily nutritional requirement of the elephants (Lewis, 1986). The research conducted at the Rajaji National Park, India revealed a 74% preference for plant species compared to 14%, 8% and 4% for grass species, shrub species and lianas (climber) species, respectively (Williams 2002). The unavailability of grasses among other reasons in the dry season could be the rationale for the selected species respectively. This species is compared to other food choices. The selection of more tree or plant species is done by the elephants in the Savannah Ecological Zone. Similar research conducted at the Manas National Park, India revealed that 18 species of flowering plants are eaten by elephants.

Comparatively, a study on the diet and foraging ecology of elephants conducted at the Shangyong National Natural Reserve, Xishuangbanna, China pointed to about 106 plant species eaten by elephants at the park (Chen et al. 2006) which shows that nutrient concentration turns to decline in the dry season for the grasses but appreciably higher in plants.

The proximate analysis of the selected plant samples (Table 1) revealed that the samples contained adequate concentrations of proximate compositions such as moisture, crude ash, crude fat, crude protein, crude fibre and Nitrogen Free Extract (Rode et al. 2006).

The proximate composition and mineral profile of herbages are controlled by several factors such as the maturity stage of the herbage, plant species involved, climate, range condition, and animal class (Gabriel et al. 2018). These factors are dominant in influencing the nutritive values of herbage. Although herbage depends on the soil for their mineral nutrients, climatic factors affect respiration, photosynthesis and metabolism to the extent that the mineral and organic matter content of herbage may be strongly modified even though they grow on the same soil (Gabriel et al. 2018). This might have accounted for the variations observed in the moisture content of Balanites aegyptiaca fruits of 14.6% ± 0.01 compared to 15.7% from the findings of Salia (2016), and this was found to be different from that reported by Jock (2011) and Ogala et al. (2018), Nigeria, of moisture contents of 7.23% and 7.16% in Balanites aegyptiaca fruits. The differences in moisture content as observed by various researchers could be due to geographical variations and time of harvest (Gabriel et al. 2018). The moisture contents (Table 1) of Terminalia laxiflora stembark, root and leaves were 9.2% ± 0.00, 10% ± 0.00 and 8.6% ± 0.00, respectively. This indicated a higher moisture content in Balanites aegyptiaca fruits than that of Terminalia laxiflora stembark.

The ash content of the animal feed is a quantitative estimation of the number of minerals present and is significant in nutritional labelling (Baraem 2017). The ash content of the samples analyzed revealed (Table 1)14.1% ± 0.01 for Ficus platyphylla stembark, 14.5% ± 0.01 for Ficus platyphylla leaves, 14.2%±0.01 for Kigelia africana leaves, 15.3% ± 0.01 for Tamarindus indica stembark and 14.7% ± 0.01 for Terminalia laxiflora stembark. These findings were higher than other findings across several parks where elephants operate. The current findings are higher than the ash content of 6.60% for Desmodium oojeinense leaves and lower than the findings of 15.54% for Desmodium oojeinense stembark in Bardia National Park, Nepal (Velde 1997).

Total fat is one of the three primary important macronutrients for the healthy growth of animals. Its presence at an appreciable level is vital to the survival of elephants due to its role in structural and metabolic activities (Pickova 2009). The total fat (Table 1) content of the selected elephants’ feeds was 7.5% ± 0.0, 4.0% ± 0.00, 3.5% ± 0.02, 1.5% ± 0.0, 4.5% ± 0.00, 4.0% ± 0.00 and 2% ± 0.00 for Detarium microcarpum leaves, Ficus platyphylla leaves, Detarium microcarpum fruits, Terminalia laxiflora root and leaves, Mitragyna inermis leaves, Balanites aegyptiaca fruits, respectively. The total fat content of Balanites aegyptiaca fruit was lower than the findings of Salia (2016) Ghana, reported 71% total fat content of Balanites aegyptiaca fruits to total fats contents by Jock (2011) Nigeria; Lohlum et al. (2012) Nigeria; Sara and Mahdi (2016) Nigeria; and Ogala et al. (2018) Nigeria. The current findings were higher than the findings of total fats of 0.74% for Desmodium oojeinense and 3.73% in the leaves of Mallotus phillipinensis as determined in the Bardia National Park, Nepal (Velde 1997). The results in Table 1 indicate an appreciable total fat content which is necessary for hormonal and cell development and structural rigidity and also as a source of energy to enable elephants’ walk long distances in search of food. The consumption of the selected plants and plant parts could be responsible for the observed energetic nature (Self-observation, January-March, 2020, Mole National Park) of the elephants at the Mole National Park.

Proteins are complex molecules and are intimately involved in practically all of life's chemical activities. The crude protein in the current study ranged from 12.0% ± 0.01 to 8.0% ± 0.01 among the samples analyzed. These findings are within the minimum requirement of 8%–12% of crude protein for elephants which is good for biological development. The highest crude protein content in the samples analyzed was observed in Ficus platyphylla stembark. Research findings of Greenwood et al. (1990) also established that the bark of plants possesses elevated levels of phloem parenchyma cells of the inner bark tissues than other parts of the plant. This might have accounted for the high crude protein content of Ficus platyphylla, as observed in Table 1. Salia (2016) reported similar findings on the crude protein content of elephant feed from Nigeria. Animal & Natural Conservation Fund (ANCF) (2011) revealed browse crude protein content of 6%–18% of crude protein for elephant feed in southern India.

Despite the high content of crude protein in the samples analyzed, some samples such as Detarium microcarpum leaves were 3.1% ± 0.00 lower than the minimum requirement of crude protein for wild elephants (8%–12%). The crude protein in the samples analyzed showed that the selected feeds of the elephants in the Savannah Ecological Zone of Ghana possess crude protein high enough to enhance the biological development of the elephants. It also revealed plants’ bark and leaves as major sources of crude protein to elephants. This could be the reason why the African elephants within the Savannah Ecological Zone browse more plant barks and leaves.

The crude fibres of the selected elephant feed analyzed were 2.2% ± 0.01, 12.8% ± 0, 3.2% ± 0.01, 4.1% ± 0.01, 2.1% ± 0.01, 1.5% ± 0.01, 2.6% ± 0.01, 2.6% ± 0.00, and 3.7% ± 0.01 for Balanites aegyptiaca fruits, Tamarindus indica bark, Ficus platyphylla bark, Climber plant (Liana), Terminalia laxiflora bark, Terminalia laxiflora root, Tamarindus indica fruits, Cassia Sieberiena root and Mitragyna inermis bark, respectively. These findings revealed a higher value of crude fibre of 12.8% ± 0 for Tamarindus indica bark and a lower value of 1.5% ± 0.01 for Terminalia laxiflora root. The fibre levels were lower than the crude fibre content of 13.50% and 67.60% reported for the Mallotus phillipinensis stembark and Desmodium oojeinense leaves, respectively (Eltringham 1982). The current results obtained were also lower than the crude fibre concentrations of 13-62% in the leaves of trees eaten by African elephants in the Kasungu National Park, Malawi. Browse, sedge and grass consumed by elephants in the Tsavo National Park, Kenya, contained 21%–49% crude fibre. Crude fibre concentrations in whole grasses, grass bases and tops, browse stems and leaves and in herbs consumed by elephants in the Queen Elizabeth National Park, Uganda, ranged from 13% to –47% (Field 1971). The presence of crude fibre in elephants’ feeds is believed to play a mechanistic role in enlarging the interior walls of the colon, allowing waste to flow more easily, making it an effective constipation remedy (Betty et al. 2016). Table 1 shows significant fibre levels necessary to aid digestion and biological metabolism as established by the research findings of Gita (2020). The difference in the range of crude fibre observed among the various parks and zoos may be due to the different geographical locations of the plants.

The nitrogen-free extract of the feed analyzed shows varying degreed among the elephant feeds (Table 1). The highest value of nitrogen-free extract was 76.6% ± 0.01 for Detarium microcarpum fruits and a lower value of 59.3% ± 0.01 for Ficus platyphylla stembark. Nitrogen-free extract is the totality of all remaining soluble carbohydrates in the feed analyzed. These findings showed a higher value of soluble carbohydrated compared to 14.54% and 72.51% for the leaves of Dalbergia sissoo and Desmodium oojeinense, respectively (Table 1). This means the leaves of plant fed by elephants within the Savannah Ecological Zone of Ghana possess better soluble carbohydrates than the leaves of Dalbergia sissoo and Desmodium oojeinense in the Bardia National Park, Nepal (Velde 1997). This means the elephant feed analyzed possesses more soluble carbohydrate that is necessary for elephants to carry out their daily activities. These differences in the proximate compositions of the elephant’s feeds might have a significant contribution to the overall health of the elephants in the Savannah Ecological Zone.

Mineral analysis gives the best indications of nutrient content to determine the reasons for the preference of the feeds by the elephants (Karyn et al., 2006). This technique provides a means of evaluating the actual nutritional status of a plant at a given time and comparing it with optimum nutrient levels.

The mineral profile in Tables 2 and 3 revealed various levels (mg/kg) of Ca, Mg, P, K and Na, Se, Zn, Fe, Mn and Cu. The highest calcium content was detected in Ficus platyphylla stembark at a concentration of 4.6 ± 0.00.

These findings were comparatively higher than the calcium content of 0.35 mg/kg–2.47 mg/kg in the browse species eaten by wild elephants in Wankie National Park, Zimbabwe (Williamson 1975). There is a higher occurrence of calcium in the stembark of the elephants’ feeds analyzed than the same for other plant parts such as the leaves, roots and fruits, as shown in Table 2. Research findings also reported a higher calcium content in most plants or tree barks than in other parts and this might be the reason why elephants prefer tree barks compared to the other parts (Kehinde et al., 2009). The calcium content of the elephants’ feed analyzed is also higher than the calcium content of 0.19 and 1.14 mg/kg in the leaves and stembark of Desmodium oojeinense, respectively in Bardia National Park, Nepal (Velde 1997).

Calcium is one of the most important elements in the structure of teeth and bones. It is needed for the development of tusk and lactating female elephants require a high amount of calcium (McCullagh 1969). Per their body weights Elephants usually feed on food containing higher calcium which aids in strong bones and normal function of nerves and muscles (McCullagh 1969). Calcium also aids parturition in elephants (Partington, 2012). In blood coagulation, calcium activates the conversion of prothrombin to thrombin and also takes part in milk clotting. It plays a vital role in enzyme activation and activates a large number of enzymes such as adenosine triphosphatase (ATPase), succinic dehydrogenase and lipase. It is also required for membrane permeability, involved in muscle contraction, the normal transmission of nerve impulses and in neuromuscular excitability. Reduced extracellular blood calcium increases the irritability of nerve tissue, and very low levels may cause spontaneous discharges of the nerve which can lead to tetany and convulsions (Soetan et al. 2010).

The higher phosphorus content of the analyzed feeds was 0.5 ± 0.01, 0.4 ± 0.01, 0.4 ± 0.01, and 0.4 ± 0.01 for Kigelia africana leaves, Mitragyna inermis, Climber plant (Liana), Terminalia laxiflora stembark and Terminalia laxiflora leaves, respectively. These values are within the minimum daily requirement of 0.2–0.15 mg/kg to maintain optimum growth of elephants (Karyn et al., 2006). The concentration of phosphorus in plants is primarily influenced by the phosphorus status of the soil, the stage of plant maturity and climate (Jumba et al. 1995). The phosphorus content of various elephants’ feeds in the Savannah Ecological Zone of Ghana was similar to the findings of browse species (Williamson 1975) eaten by elephants at the Wankie National Park, Zimbabwe (0.11 mg/kg–0.33 mg/kg).

The low values of phosphorus could be the reason why elephants dig the ground for minerals like phosphorus to balance their daily requirement (Marschner, 2012). Phosphorus plays many important roles in elephants including the production of energy in the body (Tull 1996), metabolic functions, such as energy utilization and transfer via AMP, ADP and ATP, with implications for gluconeogenesis, fatty acid transport, amino acid and protein synthesis and activity of the sodium/potassium ion pump, as well as the normal functions of rumen microbial flora (Petri et al., 1989). It is also required for the formation of the organic bone matrix and the mineralization of that matrix (Wang et al. 1985). This is particularly important for the formation of strong bones to carry the heavy weight of elephants.

There was a sodium content of 0.11 ± 0.01 in the Liana (whole plant) and Mitragyna inermis bark and a lower sodium content of 0.04 ± 0.00 in Kigelia africana bark. The findings of the current research are similar to the findings reported on the sodium content of leaves of twelve species favoured by elephants in Kasungu National Park, Malawi (0.10 mg/kg–1.25 mg/kg). However, the sodium level in the samples was relatively low compared to other minerals. This may be due to many different reasons (Morris 1980; Kemp 1971; Edmeades and O’Connor 2003). Soil licks are usually used to supplement inadequate dietary sodium. Soil lick is a common occurrence by elephants within the Savannah Ecological Zone of Ghana. Sodium is essential for electrolyte balance, and amino acid and glucose uptake (Huber et al., 2006), and the regulation of acid–base equilibrium (Mitchell 1957). Becasue of these deficiencies, the elephant to meet its recommended amount of Na+ will normally dig down the soil to look for Na+ supplement from the depth of the ground.

Magnesium and phosphorus levels were moderate in the samples analyzed (higher than sodium but lesser than calcium and potassium). Magnesium concentration may be influenced by the plant’s species and seasonal climatic conditions during plant growth (Jumba et al. 1995). Magnesium is essential for many bodily activities in elephants as it functions as a catalyst of a wide array of enzymes, facilitating the union of substrate and enzyme by first binding to one or predominantly in microsomes (Ebel and Günther 1980).

Potassium is a major contributor to the electrolyte balance and fluidity in elephants. It is also essential for the maintenance of responsiveness to stimuli and muscle tone (Ussing, 1960). The elephants’ feeds analyzed revealed an appreciable potassium content of 5.1 ± 0.01, 4.8 ± 0.00, 4.2 ± 0.00, 4.2 ± 0.00, 3.8 ± 0.01, 3.6 ± 0.01, 3.5 ± 0.00, 3.5 ± 0.01 for Mitragyna inermis bark, Climber plant (Liana), Detarium microcarpum fruits, Balanites aegyptiaca fruits, Ficus platyphylla leaves, Ficus platyphylla bark, Tamarindus indica fruits, Mitragyna inermis leaves, respectively. The results are within the recommended minimum requirements of 0.5 mg/kg–0.7 mg/kg for potassium. It can, therefore, be inferred that elephants that feed on these plant parts have the potential of enriched balancing of their electrolyte content, which is essential for physiological functions. Robinson (1985) established that given soil status, herbage potassium is influenced by the plant species, its state of maturity and the way the sward is managed.

Magnesium is mostly an intracellular cation, less tightly regulated compared to calcium, with a wider physiological range. Its roles include monitoring calcium pumps, ATPases, neural and cardiac muscle function and as a co-factor in several enzymatic reactions.

The mineral is a constituent of bones, teeth, and enzyme co-factors as established by Murray et al. (2000). The health status of the digestive system and the kidneys is significantly influenced by the amount of magnesium in the diets of elephants (Soetan et al. 2010). The highest content of magnesium in the current study was 0.4 ± 0.01 for the Climber plant (Liana) and Mitragyna inermis bark, while the lowest magnesium content was 0.1 ± 0.00 for cassia sieberiena roots, Balanites aegyptiaca fruits, Terminalia laxiflora leaves, kigelia africana bark. These findings are within the minimum requirements of 0.1 mg/kg–0.3 mg/kg for magnesium. This means the consumption of these plant species could go a long way to enrich the elephants for healthy growth and development. The absorption of magnesium is characterized by the availability of low pH and mineral rocks as a main source of magnesium in plant products. The low pH of the alimentary canal of elephants favours the absorption of magnesium in the plants eaten by these elephants. The results of the analyses are similar to the findings of 0.07 mg/kg–0.14 mg/kg of magnesium in the leaves and bark of browse species eaten by elephants in Southern India (Sukumar 1990).

There was a significant difference in zinc (Zn) concentration among all the samples analyzed except between Cassia sieberiena root and Ficus platyphylla leaves, Kigelia africana leaves and Detarium microcarpum fruits, Kigelia africana and Mitragyna inermis leaves, Kigelia africana stembark and Tamarindus indica stembark, Mitragyna inermis stembark and Balanites aegyptiaca, Detarium microcarpum fruits and Mitragyna inermis leaves, Tamarindus indica stembark and Balanites aegyptiaca fruits, Terminalia laxiflora root and stembark. There were no significant differences in the concentrations of Fe, Se and Cu among most of the samples analyzed.

Biological functional micro-nutrients (Copper (Cu), Selenium (Se), Iron (Fe) and manganese (Mn)) are important co-factors found in the structure of certain enzymes which play a key role in numerous biochemical pathways (Kehinde et al., 2009). The concentrations of these biological elements were established in the current study to be significantly low in most of the elephant feed samples analysed. These minerals are mostly present in appreciable amounts in vegetables and lower class plants than matured or higher plants because the minerals possess fewer binding properties in matured tissues and cells of higher plants, hence the lower values recorded. As the plants get matured, some of the minerals are converted into other ions and compounds and used by the plants for different metabolic processes necessary for their growth. However, continuous consumption of these plants for long periods can lead to bioaccumulation for elephants’ use to support biological activities. Some of these minerals are extracted from the soil by elephants by licking to balance their mineral requirements.

They also have a correspondingly low digestion efficiency accounting for the higher amounts of roughage in the faeces of elephants (Clauss et al. 2007).

Conclusion

The bark, leaves, fruits and root of Balanites aegyptiaca, kigelia africana, Detarium microcarpum, Terminalia laxiflora, Ficus platyphylla, cassia sieberiena, Tamarindus indica and Climber plant (Liana) contained adequate levels of crude protein, crude fibre, Total fat, Ash and Moisture obtained from the Savannah Ecological Zone, Ghana.

Cassia sieberiena root, Terminalia laxiflora bark, Terminalia laxiflora root, Ficus platyphylla bark, kigelia africana leaves, Mitragyna inermis bark, Ficus platyphylla leaves and Tamarindus indica stembark contained calcium, potassium and sodium above the minimum daily requirement for biological functioning of elephants. Detarium microcarpum leaves, Climber plant (Liana), Mitragyna inermis bark and leaves and Tamarindus indica bark contained significant levels of phosphorus and magnesium. The presence of these nutrients at higher levels might be the rationale for the selection of these plant parts as fed by the elephants within the Savannah Ecological Zone, Ghana.

The choice of herbage by elephants is governed by the need to meet the daily nutritional requirement for the healthy growth of elephants. The selection of feeds by elephants might also be in response to certain physiological changes in the life of elephants such as the developmental stage of tusk in male elephants and during lactation and gestation in female elephants.

However, the micro-nutrients Iron, copper, Zinc, selenium and manganese were all found to be significantly lower than the minimum daily requirement among all the samples analyzed. The variation in the content of nutrients and mineral elements among various parts of the plants analyzed confirms the feeding behaviour of elephants, which is to help maintain nutritional balance in elephants.

Disclosure statement

No potential conflict of interest was reported by the author(s).