TRACE ELEMENT CONCENTRATIONS IN ILL-THRIFT CALVES IN RELATION TO THE ECOLOGY OF EL-KHARGA OASIS, THE NEW-VALLEY PROVINCE, EGYPT

Document Type : Research article

Authors

1 Animal Health Research Institute, El-Dakhla, El-Wady El Gadid.

2 Department of Internal Medicine, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt.

3 Animal Health Research Institute, Assiut Laboratory

4 Animal Health Research Institute, El-Kharga, Elwady El Gadid

Abstract

Mineral imbalance in water and forages inhibit livestock production in tropical and subtropical parts of the world. This study aimed to determine trace element concentrations in blood serum of healthy and unthrifty calves and their relation with the surrounding environment including the trace element content in the soil, in addition to food and water allowed to these animals. A total of 20 yearling ill-thrift crossbred calves (group A) were chosen from El-thawra village (area A), where unthrifty calves occur. A similar number of healthy crossbred calves were chosen from El-Sabat area (area B) as a control group (group B). Results revealed that the area A soils have higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.003 and 0.004, respectively) than the area B. The area A forages have higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.2 and <0.001, respectively) than the area B. Both areas have higher Fe and Mn and lower Cu and Zn in water than the recommended levels. Values of serum Fe or Mn for both groups were within the published reference ranges. However, 10% and 55% of calves had lower Cu, and 15% and 60% had lower Zn in the groups B and A, respectively, than the reference ranges. On the other hand, blood serum of group B had significantly lower Cu (P < 0.001) and Zn (P < 0.001) than that of group A. It can be concluded that soil, forages and water in some localities in El-Kharga oasis are deficient in Cu and Zn and contain high concentrations of Fe and Mn. These mineral disturbances may directly affect the health of calves reared in these areas.

Keywords


TRACE ELEMENT CONCENTRATIONS IN ILL-THRIFT CALVES IN RELATION TO THE ECOLOGY OF EL-KHARGA OASIS, THE NEW-VALLEY PROVINCE, EGYPT

 

SAMERA A. SANOSI*; SAHAR A. ABOU EL-WAFA**; M.H. RATEB*** and                     MOSTAFA A. SALEH****

* Animal Health Research Institute, El-Dakhla, El-Wady El Gadid.

** Department of Animal Medicine, Faculty of Veterinary Medicine, Assiut University.

*** Animal Health Research Institute, Assiut Laboratory.

**** Animal Health Research Institute, El-Kharga, Elwady El Gadid.

Email: dsaharahmed2003@yahoo.co.uk

 

 

ABSTRACT

 

 

 

Mineral imbalance in water and forages inhibit livestock production in tropical and subtropical parts of the world. This study aimed to determine trace element concentrations in blood serum of healthy and unthrifty calves and their relation with the surrounding environment including the trace element content in the soil, in addition to food and water allowed to these animals. A total of 20 yearling ill-thrift crossbred calves (group A) were chosen from El-thawra village (area A), where unthrifty calves occur. A similar number of healthy crossbred calves were chosen from El-Sabat area (area B) as a control group (group B). Results revealed that the area A soils have higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.003 and 0.004, respectively) than the area B. The area A forages have higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.2 and <0.001, respectively) than the area B. Both areas have higher Fe and Mn and lower Cu and Zn in water than the recommended levels. Values of serum Fe or Mn for both groups were within the published reference ranges. However, 10% and 55% of calves had lower Cu, and 15% and 60% had lower Zn in the groups B and A, respectively, than the reference ranges. On the other hand, blood serum of group B had significantly lower Cu (P < 0.001) and Zn (P < 0.001) than that of group A. It can be concluded that soil, forages and water in some localities in El-Kharga oasis are deficient in Cu and Zn and contain high concentrations of Fe and Mn. These mineral disturbances may directly affect the health of calves reared in these areas.

 

 

Received at:15/12/2014

 

Accepted: 15/1/2015

 

Key words: Ill-thrift calves, Trace element, El-kharga the New-valley province.

 

 


INTRODUCTION

 

Mineral imbalance in water, soil and forages inhibit livestock production in tropical and subtropical parts of the world. One of the greatest challenges in pasture management is meeting the nutrient requirements of the ruminant due to variable forage quality. Previous research has shown that location and soil parent material were significant factors contributing to mineral uptake by forages (Suttle, 2010).

 

By the beginning of the 21st century, the plant life in the oases of Egypt has completely changed. About 500,000 acres are expected to be reclaimed and cultivated in the western desert after transferring the Nile water to these areas through the Toschka canal.

 

Relations between the geochemical nature of soils and their parent materials and the occurrence of nutritional deficiencies and excesses in grazing livestock have been documented since the 1960s and earlier (Miller and Stake, 1974). The scientists now have more advanced tools to facilitate the understanding of processes in the soil–plant–animal ecosystem that influence and control the supply of essential nutrient elements (Thornton, 2002).

 

For several decades, a major goal in the veterinary research has been to assess mineral status of animals, in which there are important practical problems (McDowell, 1997). Nowadays, mineral metabolism has reached a new importance and received a new stimulus with the development of instrumental tools and veterinary studies. It has been established that the status of these elements in animal body is the mirror image of the health, growth, productive and reproductive ability of livestock. The lack of adequate amounts of minerals is the major constraint limiting livestock production worldwide (Underwood and Suttle, 1998; Suttle, 2010).

 

McDowell (2003) concluded that the micronutrient deficiencies is the most commonly encountered in the field are of a marginal nature, often with non-specific ill thrift as the only sign of a disorder. Therefore, tests of blood and tissue are relied on to identify which micronutrient might be limiting productivity. For many of the micronutrients, biochemical changes in blood precede dysfunction, so monitoring of these changes provides early warning.

 

New-Valley is an arid inland tropical area. Soil nature is sandy limestone with low humus and low annual precipitation. Areas of such conditions are disturbed in mineral constituents and these minerals are readily leached from these soils by irrigation. Consequently, these possible disturbances in minerals in these soils may be directly reflected on mineral concentrations in the agricultural and local foods allowed to animals in this area (Khalil et al., 2004). In turn these disturbances of minerals in soil and plant may be directly or indirectly affect the concentrations of these minerals in rearing animals and their health (Suttle, 2010).

 

Under these circumstances, however, mineral status of grazing ruminants is not well quantified under the local environment of the New-Valley region and the precise impacts of deficiencies are uncertain.

 

This study aimed to determine trace element concentrations in blood serum of healthy and unthrifty calves and their relation with the surrounding environment including the trace element content in the soil, in addition to food and water allowed to these animals.

 

MATERIALS and METHODS

 

Animals:

Crossbred calves (Friesian x Balady) in some localities in El-Kharga oasis are suffering from ill-thrift, poor growth, dullness and harsh coat. A total of 20 yearling ill-thrift crossbred calves (group A) were chosen from El-Thawra village (area A), where unthrifty calves occur. A similar number of healthy crossbred calves were chosen from El-Sabat area (area B) as a control group (group B). All calves were subjected to careful clinical and laboratory examination to judge their health status, and to ensure the absence of debilitating diseases or parasites.

 

Sampling:

Five soil samples at 20–30 cm depth were taken from pastures used for animal feeding in the studied areas. Samples were air-dried, ground, mixed and sieved. One gram from each sample was placed in a 125 ml conical flask and 20 ml of 0.005 M ammonium bicarbonate diethylene-triamine-penta-acetic acid (AB-DTPA) solution was added to it. After shaking the samples for 15 min, they were filtered through Whatman ashless filter paper. A clear supernatant was obtained by centrifuging for 20 min at 3000 rpm and stored in plastic bottles according to methods described by AOAC (1995).

 

Five samples from Barseem Hegazi (Medicago sativa), the main forage used for feeding of calves in these areas, were collected from the same points where soil samples were collected in the two areas. These samples were washed with 1% HCI, followed by four washes with distilled water to remove dust particles. These samples were then oven-dried at 70 ºC and ground to a powder, stored in clean, dry brown paper bags for further analysis (AOAC, 1995). The dried ground material (0.5 g) was digested in sulphuric acid and hydrogen peroxide according to the method of Wolf (1982).

 

Water was sampled directly from the well opening or the main water source in the studied areas to represent a non-soil contaminated sample. A clean, sterile one liter capacity bottles were used and crocked well after it were filled with water. These bottles were sent immediately to the laboratory for biochemical analysis according to methods described by AOAC (1995).

 

Blood was drawn from the jugular vein of all the selected calves in centrifuge tubes. The blood was allowed to coagulate and the harvested serum was stored at -20°C until processing.

 

Trace elements analysis:

Micro-nutrients (Fe, Cu, Zn and Mn) in soil, pasture and water were determined in the Regional Laboratory for Soil Analysis, New-Valley governorate, using atomic absorption spectrophotometer (GBC 932 AA) air-acetylene type according to manufacture instructions.

 

For determination of micro-minerals in serum, two mls of serum were digested with a 4 ml mixture of perchloric acid and nitric acid (1:1) using hot plates. After digestion, the volume was made up to 25 ml with bi-distilled water for determination of the micro-minerals (Fe, Cu, Zn and Mn) using atomic absorption spectrophotometer (GBC 932 AA) air-acetylene type according to manufacture instructions.

 

Statistical analysis:

Data were analyzed using the packagedSPSSprogram for windows version 10.0.1 (SPSS Inc., Chicago, IL.). Differences between groups were determined by the one way analysis of variance (ANOVA) followed student's t test. Data were presented as least squares means (LSM) and standard error of means (±SEM). Significance level was set at P < 0.05.

 

RESULTS

 

Extractable mineral concentrations of soils:

The mean values (ppm ± SE) of Fe, Cu, Zn and Mn concentrations in the area A, B soils are illustrated in table 1. The area A has significantly higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.003 and 0.004, respectively) than the area B.

 

Mineral concentrations of forage:

The mean values (ppm ± SE) of Fe, Cu, Zn and Mn concentrations in forages in the examined areas are shown in table 2. The area A forages have significantly higher Fe and Mn (P < 0.001) and lower Cu and Zn (P < 0.2 and <0.001, respectively) than the area B.

 

Mineral concentrations of water:

The values of trace elements in water in the studied areas are presented in table 3. Both areas have higher Fe and Mn and lower Cu and Zn than the recommended levels by Schlink et al. (2010).

 

Mineral concentrations in calves:

The mean values of concentrations of Fe, Cu, Zn and Mn concentrations in serum of calves are illustrated in table 4 and Fig 1. It was noticed also that none of the studied calves had lower values of serum Fe or Mn than the published reference range. However, 10% and 55% of calves had lower Cu, and 15% and 60% had lower Zn in the groups B and A, respectively, than the reference ranges. On the other hand, blood serum of group A had significantly lower Cu (P < 0.001) and Zn (P < 0.001) than that of group B.

 

 

Table 1: Extractable trace element concentrations (ppm) of soils (mean±SE).

 

Mineral

Area A

Area B

P-value

Reference range*

Fe

895.9±0.24

412.1±0.14

<0.001

1-10

Cu

0.11±0.02

0.19±0.05

0.003

0.20

Zn

0.71±0.09

0.91±0.09

0.004

1.0

Mn

2400.1±104.3

397.3±55.2

<0.001

300-1100

 

 * Suttle (2010).

 

Table 2: Trace element concentrations (ppm) of forage (mean±SE).

 

Mineral

Area A

Area B

P-value

Reference range*

Fe

394±8.4

201.6±6.1

<0.001

50.0

Cu

3.09±0.76

4.67±0.81

<0.001

5.00

Zn

5.88±0.29

6.41±0.21

0.024

7-10

Mn

442.1±41.1

201.3±23.3

<0.001

86

 

*Suttle (2010).

 

Table 3: Trace element concentrations (ppm) in water.

 

Mineral

Area A

Area B

Maximum level*

Fe

4.983

5.144

0.50

Cu

0.002

0.002

0.2

Zn

0.0039

0.0041

0.5

Mn

4.300

2.700

0.5

 

  * Schlink et al. (2010)

Table 4: Concentrations of minerals (μg/dl) in blood plasma of calves (mean±SE).

 

 

Group A

Group B

P-

value

RR*

Mean±SE

% of calves less than RR

Mean±SE

% of calves less than RR*

Fe

159.2±8.5

00 %

162.5±9.6

00 %

0.066

70-230

Cu

54.1±4.2

55 %

71.41±3.8

10 %

0.001

>60

Zn

49.4±3.1

60 %

82.21±2.9

15 %

0.001

>60

Mn

0.32±0.08

00%

0.27±0.09

00%

0.001

0.15-0.28

 

* RR: Reference range according to Suttle (2010).

 

 

 


DISCUSSION

 

Micronutrient deficiencies most commonly encountered in the field are of a marginal nature, often with non-specific ill thrift as the only sign of a disorder. Therefore, studies on the geochemical nature of soils and their parent materials in addition to tests of animal’s blood are relied on to identify which micronutrient might be limiting productivity. For many of the micronutrients, biochemical changes in blood precede dysfunction, so monitoring of these changes provides early warning (Suttle, 2010).

 

The soil of area A has a significantly higher Fe and Mn (P < 0.001) and a lower Cu and Zn (P < 0.03 and 0.004, respectively) than the area B. In addition, the concentrations of Fe and Mn are higher than the recommended levels cited by Thornton (2002) and Suttle (2010). Furthermore, Cu contents is lower than the critical levels cited by Suttle (2010). Our results in this respect concur with the findings of Khalifa     et al. (1996), Abdel Aziz (1998) and Khalil et al. (2004). Mehana and Abdul Wahid (2002) found that most of the reclaimed areas, which planned to be cultivated in Egypt, are sandy soils with alkaline pH.

 

Area A forages has higher concentrations of Fe and Mn than the forages of area B, and both areas has higher Fe and Mn than the recommended levels cited by Thornton (2002) and Suttle (2010). On the other hand, Area A forages has lower concentrations of Cu and Zn than the forages of area B, and both area has lower Cu and Zn than the recommended levels cited by Thornton (2002) and Suttle (2010).

 

Mineral concentrations in water in the studied areas have the same trend of that of the soil and forage. Fe and Mn content in water are higher than the permissible levels cited by Schlink et al. (2010) and WHO (2011). Mn content in water of the area A is higher than the area B.

 

The physiologic effects of the essential mineral elements depend on the level of intake. There is a range of intake, the so-called safe and adequate range, which provides optimal function. At intakes progressively below this range there is graded decrease in function until overt signs of deficiency appear (McDowell, 1997).

 

In the present study, trace element concentrations in the soil, forages and water directly reflected on their concentrations in the serum of calves grazing on these areas. Both plasma Fe and Mn were within the normal reference ranges cited by Thornton (2002) and Suttle (2010). However, 55 % and 60 % of calves of group A had lower Cu and Zn, respectively, than the reference range compared with 10 % and 15 %, in calves of group B, respectively. kerr (2002) reported that forage mineral composition can have a significant effect on animal performance and health, as they are often not in balance with the nutrient requirements of the animals. Hypocuprosis and hypozencosis are the major causes of anorexia, growth retardation, anemia and harsh coat in calves (Suttle, 2010).

 

Manganese and iron excess in the diet can trap sulphate in the rumen and impair Cu and Zn metabolism by binding of sulfide ions (S2−) to soluble Fe from rumen producing iron sulfide (FeS), preventing Cu to bind to S2−, hindering thus the absorption of this element, binding of Cu to insoluble iron compounds, and by the utilization of nonspecific transporters of multiple metals by soluble Fe, thereafter preventing the Cu and Zn to bind to this carries and be absorbed (Hansen et al., 2006; Hansen and Spears, 2008 and Hansen et al., 2009). In pastures containing 140–200 mg Mn kg−1 DM, the growth rate is significantly depressed and reduction in plasma iron was evident despite the fact that the pastures contained 1100–2200 mg Fe kg−1 DM (Suttle, 2010).

 

It can be concluded that soil, forages and water in some localities in El-Kharga oasis are deficient in Cu and Zn and contain high concentrations of Fe and Mn. These mineral disturbances may directly affect their concentrations in animal tissues and impair the health of calves reared in these areas.

 

REFERENCES

 

Abdel Aziz, S.H. (1998): Pedological studies on some soils of Wadi El Assiuty, Assiut, Egypt. Ph. D. thesis, Fac. of Agric. Assiut Univ.

AOAC (1995): Official Methods of Analysis of Association of Official Analytical Chemists, vol. 1, 16th ed. AOAC International, Arlington, VA, pp. 4/1–4/30.

Hansen, S.L.; Ashwell, M.S.; Legleiter, L.R.; Fry, R.S.; Lloyd, K.E. and Spears, J.W. (2009): The addition of high manganese to a copper-deficient diet further depresses copper status and growth of cattle. British Journal of Nutrition 101, 1068–1078.

Hansen, S.L. and Spears, J.W. (2008): Impact of copper deficiency in cattle on proteins involved in iron metabolism. FASEB Journal 22, 443–445.

Hansen, S.L.; Spears, J.W.; Lloyd, K.E. and Whisnant, C.S. (2006): Growth, reproductive performance, and manganese status of heifers fed varying concentrations of manganese. J Anim Sci. 84: 3375-3380.

Kerr, M.G. (2002): Veterinary Laboratory Medicine 2nd ed. Blackwell Science, UK.

Khalifa, E.M.; El-Desoky, A.M.; Gameh, M.A. and Faragallah, M.E. (1996): Status of some micronutrients and their relations to mineral composition of the Nile Valley-Desert interference zone soils, east of Assiut city. Assiut J. Agric. Sci. 27: 108-127.

Khalil, M.N.; Mohammad, I.R.; Metwally, M.A. and Abdel-Khalik, M.A. (2004): Distribution of some nutrients in certain soils of the New Valley governorate. Zagazig J. Agric. Res. 31: 2287-2314.

McDowell, L.R. (2003): Minerals in Animal and Human Nutrition, 2nd Ed. Elsevier Science, Amsterdam.

McDowell, L.R. (1997): Minerals for Grazing Ruminants in Tropical Regions. 3rd Ed., Department of Animal Science Bulletin, Center for Tropical Agriculture, University of Fla, Gainesville.

Mehana, T.A. and Abdul Wahid, O.A. (2002): Associative Effect of Phosphate Dissolving Fungi, Rhizobium and Phosphate Fertilizer on Some Soil Properties, Yield Components and the Phosphorus and Nitrogen Concentration and Uptake by Vicia faba L. Under Field Conditions. Pakistan Journal of Biological Sciences 5: 1226-1231.

Miller, W.J. and Stake, P.E. (1974): Uses and limitation of biochemical measurements in diagnosing mineral deficiencies. In: Proceedings of Georgia Nutrition Conference for Feed Industry, University of Georgia, Athens, GA, USA, pp. 25–37.

Schlink, A.C.; Nguyen, M.-L. and Viljoen, G.J. (2010): Water requirements for livestock production: a global perspective. Rev. sci. tech. Off. int. Epiz., (OIE) 2010, 29, 603-619.

Suttle, N.F. (2010): Mineral Nutrition of Livestock, 4th Ed. CABI Head Office, Oxford.

Thornton, I. (2002): Geochemistry and the mineral nutrition of agricultural livestock and wildlife. Applied Geochemistry 17, 1017–1028

Underwood, E.J. and Suttle, N.F. (1998): The Mineral Nutrition of Livestock, 3rd ed. Commonwealth Agricultural Bureaux. Farnham Royal, Slough, UK.

WHO (2011): Manganese in Drinking-water. Background document for development of WHO Guidelines for Drinking-water Quality. Pp 3-9.

Wolf, B. (1982): A comprehensive system of leaf analysis and its use for diagnosing crop nutrient status. Commun. Soil Sci. Plant Anal., 13: 1035-1059.

 

 

ترکيز العناصر النادرة في العجول الهزيلة وعلاقتها ببيئة الواحات

الخارجة - محافظة الوادي الجديد

 

سميرة أحمد سنوسي  ،  سحر أحمد أبوالوفا  ،  محمد حجازي راتب  ،  مصطفى أحمد صالح

Email: dsaharahmed2003@yahoo.co.uk

 

اختلال توازن المعادن في المياه والحشائش يؤثر على الإنتاج الحيواني في المناطق الاستوائية وشبه الاستوائية من العالم. هدفت هذه الدراسة إلى تحديد ترکيز العناصر النادرة في مصل دم العجول السليمة والهزيلة وعلاقتها بترکيز تلک المعادن في البيئة المحيطة بما في ذلک محتوى العناصر النادرة في التربة، بالإضافة إلى الغذاء والماء المتاح لهذه الحيوانات. وقد تم اختيار 20 من العجول الهجين الهزيلة عمره سنة تقريبا (المجموعة A) من قرية الثورة (منطقة A)، حيث توجد العجول الهزيلة. وقد تم اختيار عدد مماثل من العجول الهجين السليمة من منطقة السبط (منطقة B) کمجموعة ضابطة (المجموعة B). أوضحت النتائج أن تربة والحشائش في المنطقة A أعلى في ترکيز الحديد والمنغنيز وأقل في ترکيز النحاس والزنک من المنطقة B. وأظهرت النتائج أيضا أن المياه في کلتا المنطقتين تحتوى على نسبة أعلى في ترکيز الحديد والمنغنيز وعلى نسبة أقل في ترکيز النحاس والزنک من المستويات الموصى بها. کانت قيم الحديد أو المنغنيز في مصل المجموعتين من العجول ضمن نطاق المرجعية المنشورة. ومع ذلک، کان 10٪ و 55٪ من العجول تحتوى على ترکيز منخفض من النحاس ، و 15٪ و 60٪ تحتوى على ترکيز منخفض من الزنک عن النطاقات المرجعية في المجموعةB  و A على التوالي. من ناحية أخرى، کان مصل الدم في المجموعة A أقل في محتوى النحاس والزنک عن المجموعة B. يمکن أن نخلص إلى أن التربة واالحشائش والمياه في بعض المناطق في واحة الخارجة تعاني من نقص في النحاس والزنک وتحتوي على ترکيزات عالية من الحديد والمنجنيز. هذه الاضطرابات المعدنية قد تؤثر بشکل مباشر على صحة العجول المرباة في هذه المناطق.

REFERENCES
 
Abdel Aziz, S.H. (1998): Pedological studies on some soils of Wadi El Assiuty, Assiut, Egypt. Ph. D. thesis, Fac. of Agric. Assiut Univ.
AOAC (1995): Official Methods of Analysis of Association of Official Analytical Chemists, vol. 1, 16th ed. AOAC International, Arlington, VA, pp. 4/1–4/30.
Hansen, S.L.; Ashwell, M.S.; Legleiter, L.R.; Fry, R.S.; Lloyd, K.E. and Spears, J.W. (2009): The addition of high manganese to a copper-deficient diet further depresses copper status and growth of cattle. British Journal of Nutrition 101, 1068–1078.
Hansen, S.L. and Spears, J.W. (2008): Impact of copper deficiency in cattle on proteins involved in iron metabolism. FASEB Journal 22, 443–445.
Hansen, S.L.; Spears, J.W.; Lloyd, K.E. and Whisnant, C.S. (2006): Growth, reproductive performance, and manganese status of heifers fed varying concentrations of manganese. J Anim Sci. 84: 3375-3380.
Kerr, M.G. (2002): Veterinary Laboratory Medicine 2nd ed. Blackwell Science, UK.
Khalifa, E.M.; El-Desoky, A.M.; Gameh, M.A. and Faragallah, M.E. (1996): Status of some micronutrients and their relations to mineral composition of the Nile Valley-Desert interference zone soils, east of Assiut city. Assiut J. Agric. Sci. 27: 108-127.
Khalil, M.N.; Mohammad, I.R.; Metwally, M.A. and Abdel-Khalik, M.A. (2004): Distribution of some nutrients in certain soils of the New Valley governorate. Zagazig J. Agric. Res. 31: 2287-2314.
McDowell, L.R. (2003): Minerals in Animal and Human Nutrition, 2nd Ed. Elsevier Science, Amsterdam.
McDowell, L.R. (1997): Minerals for Grazing Ruminants in Tropical Regions. 3rd Ed., Department of Animal Science Bulletin, Center for Tropical Agriculture, University of Fla, Gainesville.
Mehana, T.A. and Abdul Wahid, O.A. (2002): Associative Effect of Phosphate Dissolving Fungi, Rhizobium and Phosphate Fertilizer on Some Soil Properties, Yield Components and the Phosphorus and Nitrogen Concentration and Uptake by Vicia faba L. Under Field Conditions. Pakistan Journal of Biological Sciences 5: 1226-1231.
Miller, W.J. and Stake, P.E. (1974): Uses and limitation of biochemical measurements in diagnosing mineral deficiencies. In: Proceedings of Georgia Nutrition Conference for Feed Industry, University of Georgia, Athens, GA, USA, pp. 25–37.
Schlink, A.C.; Nguyen, M.-L. and Viljoen, G.J. (2010): Water requirements for livestock production: a global perspective. Rev. sci. tech. Off. int. Epiz., (OIE) 2010, 29, 603-619.
Suttle, N.F. (2010): Mineral Nutrition of Livestock, 4th Ed. CABI Head Office, Oxford.
Thornton, I. (2002): Geochemistry and the mineral nutrition of agricultural livestock and wildlife. Applied Geochemistry 17, 1017–1028
Underwood, E.J. and Suttle, N.F. (1998): The Mineral Nutrition of Livestock, 3rd ed. Commonwealth Agricultural Bureaux. Farnham Royal, Slough, UK.
WHO (2011): Manganese in Drinking-water. Background document for development of WHO Guidelines for Drinking-water Quality. Pp 3-9.
Wolf, B. (1982): A comprehensive system of leaf analysis and its use for diagnosing crop nutrient status. Commun. Soil Sci. Plant Anal., 13: 1035-1059.