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TISSUE MINERAL ANALYSES OF WILDLIFE AS INDICATION OF THE

MINERAL NUTRITIONAL SITUATION IN REGIONS

 

  J.B.J. van Ryssen1 and J.H. Hoon2


1Department of Animal & Wildlife Sciences, University of Pretoria, Pretoria, South Africa

2 Grootfontein ADI, Private Bag X529, Middelburg 5900, South Africa

E-mail: php%20echo%20mailMe%28%22jvryssen%2Cup.ac.za%22%2C%22JBJ%20van%20Ryssen%22%2C%22Contact%20JBJ%20van%20Ryssen%22%29%3B%20

 


ABSTRACT

Hepatic concentrations of some minerals can indicate the nutritional status of animals for the element. Without consumption of mineral supplements, this would indicate the mineral nutritional status in geographical regions. Since livestock often receive supplements, tissues from wildlife were used in this study. South African hunters have collected liver samples from impala (Aepyceros melampus melampus), springbok (Antidorcas marsupialis) and blesbok (Damaliscus pygargus phillipsi) and forwarded them to the laboratory for copper (Cu), selenium (Se) and manganese (Mn) analyses. Between regions large differences in concentrations were recorded: In springbok, high concentrations of hepatic copper and selenium in the Karoo region; in blesbok low concentrations of Se and Cu in the highland sourveld; in the Bushveld regions of northern Limpopo Province the Cu and Se concentrations in impala livers varied between areas. Irrespective of its limitations this approach can supply useful information on the mineral nutritional status of herbivores in a region.

 

INTRODUCTION

Many regions of the world have been mapped according to the likelihood of encountering mineral deficiencies or toxicities in livestock consuming the food produced in the specific regions (Oldfield, 1999). Knowledge of the mineral nutritional status of animals in a region is valuable in deciding on supplemental feeding strategies to follow. An evaluation of the rock and soil and water composition and soil pH is a useful starting point in such a prediction.  However, since a large number of factors can interfere with the absorption and bioavailability of an element, a more reliable indicator would be the mineral content of tissues or fluid of animals that consumed the plants, provided that the concentration of the mineral in the tissue follows more or less a linear increase with an increase in intake of the element. Domestic livestock often receive mineral supplements which would compromise tissue concentrations as indication of mineral status of a region.  Allowing for a number of limitations, tissue and fluid analyses of herbivorous game species that did not consume mineral supplements could be used for this purpose. Webb et al. (2001) used the liver analyses data from 660 buffalo culled in the Kruger National Park (KNP) in South Africa to plot the relative distribution of their selenium (Se) and (Cu) nutritional status in the Park. Gummow et al. (1991) and Grobler & Swan (1999) could use Cu liver concentrations of impala in the KNP to identify a serious Cu pollution problem in an area close to a copper mine. The objective of this study was to analyse liver samples from game in specific areas of South Africa to get an indication of the trace element nutritional status of herbivores in different regions.

 

MATERIAL AND METHODS

South African hunters were requested through hunters’ magazines and personally to collect liver samples from impala (Aepyceros melampus melampus), springbok (Antidorcas marsupialis) and blesbok (Damaliscus pygargus phillipsi).  Because these species are not distributed throughout the country, different species were used because of their abundance in specific regions. Preference was given to areas where little data were available in the mapping of the Se status of the country (Van Ryssen, 2001). Hunters were requested to record the geographic location, sex and approximate age of the animals. A maximum of 10 samples was required per location, though often only a few samples were collected.

 

Frozen or formalin treated liver samples were delivered to the UP Nutrilab where Cu, Se and manganese (Mn) analyses were performed on them. Copper and Mn concentrations were determined using atomic absorption spectrometry and Se using a hydride generator attachment on the atomic absorption spectrometer.

Mineral status of the animals was based on sufficiency / deficiency criteria used for cattle and sheep (Grace, & Clark, 1991; Puls, 1994; Underwood & Suttle, 1999). Unfortunately, these authorities differ significantly in what concentrations they consider as indicative of a marginal deficiency. Values used to indicate a marginal deficiency were: copper: < 75 mg/kg DM (Puls, 1994) or < 20 mg/kg DM (Underwoord & Suttle, 1999); manganese: < 6 mg/kg DM (Puls, 1994; Underwood & Suttle, 1999); selenium: < 400 μg/kg DM (Puls, 1994) or < 107 μg/kg DM (Grace, & Clark, 1991; Underwood & Suttle, 1999). 

 

RESULTS

Table 1  Concentration (mean ± standard deviation, STD) of copper, selenium and manganese in the livers of three game species in different regions of South Africa

Copper

Species

N

Mean

STD

Deficient range

< 60 mg/kg

< 20 mg/kg

mg/kg DM

%

%

Impala*

67

120

65

33

3

Blesbok**

70

83

51

43

13

Springbok***

58

116

52

16

2

Selenium

Species

N

Mean

STD

< 400 μg/kg

< 107 μg/kg

μg/kg DM

%

%

Impala*

67

774

458

15

0

Blesbok*

70

291

95

92

1.3

Springbok***

58

1263

588

10

1.4

Manganese

Species

N

Mean

STD

< 6 mg/kg

mg/kg DM

%

Impala*

67

10.4

3.0

3

Blesbok**

70

12.4

1.8

0

Springbok***

58

8.4

3.0

24

* Impala  - Savanna Bushveld, (northern Limpopo Province) 

** Blesbok - Highland sour grassveld (eastern Mpumalanga and Free State Provinces)

*** Springbok - Shrubveld, semi desert (Karoo and Kalahari in Northern Cape Province)

 

DISCUSSION

It was evident that there is very little overlap in habitat between the three game species.  A further problem is that eating habits of the species differ, with impala and springbok being intermediate mixed feeder, i.e. browsing and grazing, while the blesbok is mainly a grazer.  Therefore, the composition of their diets would have been quite different. This would have a confounding effect on the interpretation of the results.  Furthermore, it is practically unknown what hepatic concentrations indicate a deficiency or toxicity in these species, and the criteria from domestic animals had to be used. 

 

However, differences between regions were quite distinct and corresponded well with soil characteristics indicative of the availability of mineral elements present. This study confirmed that in the Karoo (semi desert) region of South Africa it is unlikely that herbivores would suffer from a Cu deficiency, in agreement with the map published by Bath (1979) and a Se deficiency, supporting the Se map published by Van Ryssen (2001). The Cu and Se concentrations in the livers of the impalas in the savanna (bushveld) regions of northern Limpopo Province differed between locations, though, in general, herbivores are unlikely to suffer from a Cu or Se deficiency in this region. Animals grazing on highland sour grassveld of the eastern Free State Province and Mpumalanga had relatively low concentrations of Se in their livers. They are also likely to suffer from a Cu deficiency especially in certain areas (Warden, Bethlehem) of the eastern Free State.

 

In general, in ruminants only Cu and Se concentrations follow a linear increase in the liver with an increase in intake of the element. However, no information is available to confirm if hepatic Cu and Se accumulation in these game species is similar to that in cattle or sheep.  Further studies are required to establish this and differences between game species. However, from this investigation it would appear that their response in the liver to Cu and Se intakes could be similar to that of cattle and sheep.

 

REFERENCES

Bath, G.F., 1979. Enzootic icterus – A form of chronic copper poisoning. Journal of the South African Veterinary Association 50, 3-14.

Grace, N.D. & Clark, R.G., 1991. Trace element requirements, diagnosis and prevention of deficiencies in sheep and cattle. In: Physiological Aspects of Digestion and Metabolism in Ruminants. Eds Tsuda, T., Sasaki, Y. & Kawashima, R. Academic press, NY. pp. 321-346.

Grobler, D.G. & Swan, G.E., 1999.  Copper poisoning in the Kruger National Park: Field investigation in wild ruminants. Onderstepoort Journal of Veterinary Research 66, 157-168.

Gummow, B., Botha, C.J., Basson, A.T. & Bastianello, S.S., 1991. Copper toxicity in ruminants: Air pollution as a possible cause. Onderstepoort Journal of Veterinary Research 58, 33-39.

Oldfield, J.E., 1999. Selenium World Atlas. Published by Selenium-Tellurium Development Association, Grimberger, Belgium.

Puls, R., 1994. Mineral Levels in Animal Health. Diagnostic data. 2nd Ed. Sherpa Int, Canada.

Underwood, E.J., Suttle, N.F., 1999. The Mineral Nutrition of Livestock. 3rd Ed. CABI Publ., Oxon, UK.

Van Ryssen, J.B.J., 2001. Geographical distribution of the selenium status of herbivores in South Africa. South African Journal of Animal Science 31, 1-7.

Webb, E.C., van Ryssen, J.B.J., Erasmus, E.A. & McCrindle, M.E., 2001. Copper, manganese, cobalt and selenium concentrations in liver samples from African buffalo (Syncerus caffer) in the Kruger National Park. Journal of Environmental Monitoring 3, 583-585.