Some biochemical parameters of Cerebrospinal fluid and Serum in clinically healthy Sudanese Cattle

Authors

1 Department of Biomedical Science, College of Veterinary Medicine, Sudan University of Science and Technology, Sudan

2 Department of Pathology, Faculty of Veterinary Medicine, University of Khartoum Sudan

Abstract

This study was undertaken to determine the values of some physiochemical parameters of cerebrospinal fluid (CSF) of healthy Sudanese steers and compare them with their corresponding serum values. The experimental animals were thirty clinically normal steers presented to the Slaughter House of The Animal Production Research Centre at Kuku.
          Cerebrospinal fluid samples were taken from the cisterna magna and blood was withdrawn from the jugular vein. Some electrolytes, metabolites  and enzymes activities were determined in cerebrospinal fluid and serum. The mean values for CSF constituents were as follows; total protein(TP) (6.45±0.03mg/100ml), albumin  (2.57±0.02mg/100ml), urea (17.97±0.25mg/100ml), Creatinine (1.17±0.021mg/100ml), glucose(47.67±0.26   mg/100ml), Na(104.87±1.57mmol/L), K(3.09±0.03mmol/L), Ca(5.48±0.03mmolL), and Mg (1.49±0.03mg/100ml) ,and the activities of the enzymes ALP (75.10 ±0.51 U/L), AST(20.13±0.37 U/L) and ALT(5.50±0.18 U/L) and their corresponding values in serum were (7920±0.03mg/100ml)(3920±0.03mg/100ml);(27.27±0.26mg/100ml); (1.36±0.02g/ml);(48.18±0.28mg/100ml);( 113.20±0.99 mmol/L);( 3. 66±0.03 mmol/L) ;( 7. 72±0.02 mmol/L) ;( 47.57±0.48 µg/100ml) , (1.28±0.02mg/100ml);( 84.08±0.29 U/L);( 30.73±0.61 U/L) and (10.17±0.44 U/L) respectively. The mean vlues of all the studied parameters, except of Mg, were significantly lower in CSF than those in serum. The obtained results were discussed with previous reports in cattle and other domestic animals. The values reported in this study can add to the reference value for Sudanese cattle.

Keywords


Some biochemical parameters of Cerebrospinal fluid and Serum in clinically healthy Sudanese Cattle

Omer, S. A (1); Ahmed, S. H;(1) and  Gameel, AA (2).

1- Department of Biomedical Science, College of Veterinary Medicine, Sudan University of Science and Technology, Sudan.

2- Department of Pathology, Faculty of Veterinary Medicine, University of KhartoumSudan.

Summary

         This study was undertaken to determine the values of some physiochemical parameters of cerebrospinal fluid (CSF) of healthy Sudanese steers and compare them with their corresponding serum values. The experimental animals were thirty clinically normal steers presented to the Slaughter House of The Animal Production Research Centre at Kuku.

          Cerebrospinal fluid samples were taken from the cisterna magna and blood was withdrawn from the jugular vein. Some electrolytes, metabolites  and enzymes activities were determined in cerebrospinal fluid and serum. The mean values for CSF constituents were as follows; total protein(TP) (6.45±0.03mg/100ml), albumin  (2.57±0.02mg/100ml), urea (17.97±0.25mg/100ml), Creatinine (1.17±0.021mg/100ml), glucose(47.67±0.26   mg/100ml), Na(104.87±1.57mmol/L), K(3.09±0.03mmol/L), Ca(5.48±0.03mmolL), and Mg (1.49±0.03mg/100ml) ,and the activities of the enzymes ALP (75.10 ±0.51 U/L), AST(20.13±0.37 U/L) and ALT(5.50±0.18 U/L) and their corresponding values in serum were (7920±0.03mg/100ml)(3920±0.03mg/100ml);(27.27±0.26mg/100ml); (1.36±0.02g/ml);(48.18±0.28mg/100ml);( 113.20±0.99 mmol/L);( 3. 66±0.03 mmol/L) ;( 7. 72±0.02 mmol/L) ;( 47.57±0.48 µg/100ml) , (1.28±0.02mg/100ml);( 84.08±0.29 U/L);( 30.73±0.61 U/L) and (10.17±0.44 U/L) respectively. The mean vlues of all the studied parameters, except of Mg, were significantly lower in CSF than those in serum. The obtained results were discussed with previous reports in cattle and other domestic animals. The values reported in this study can add to the reference value for Sudanese cattle.

Key words: Sudanese cattle, cerebrospinal fluid, Serum, biochemical profile

Corresponding author:shadiaatti@sustech.edu

Introduction

Cerebrospinal fluid (CSF) is a clear ultrafilterate of plasma, mainly produced by the choroid plexus and ependymal lining cells of the brain ventricles. It probably serves as a nutritive medium for the brain and spinal cord, provides mechanical support, regulates the chemical environment of the brain and acts as vehicle for transport of biologically active compounds (Kaneko et al., 1997).

CSF composition is strongly dependent on that of blood and is a reflection of the blood plasma constituents. Its composition is subject to various environmental, physiological and pathological conditions (Al Sagair et al., 2005, Wells, et al.1992.). Normal values of CSF have been reported for many animal species including cattle, sheep, camels, and companion animals, (Stocker et al., 2002; Ameri and Mousavian, 2007; Ahmed, et al, 2009 and Di Terlizzi and Platt, 2009).

The examination of the CSF has become an integral part of the assessment of the critically ill neurological or neurosurgical people (Venkatesh et al., 2002). Also changes in CSF constituents related to CNS disorders, have been investigated in cattle (Tyler, et al., 1993, Braun et al., 2003, and Stoko, et al. 2009), horses (Sofaly, et al., 2002) and dogs (Garma and Tyler, 1999)

In the Sudan, there seems to be lack of information on normal values of CSF constituents in animals and standard values set elsewhere are usually consulted in neurological investigations. The objective of this study was to establish normal range values for CSF for Sudanese cattle in relation to serum which may be useful in clinical investigations of CNS diseases and in other pathophysiological studies.

Materials and Methods

Animals:

 Serum and cerebrospinal fluid samples were taken from, thirty Sudanese (Baggara) steers, 2-3 years old and weighing between 260 and 300 kg. The animals were designated healthy based on the results of anti mortem examination, before slaughter at the Animal Production Research Centre, Hilat Kuku.

Sample Collection

1. CSF collection:

CSF samples (5ml) were collected from each animal into clean sterile containers, immediately after slaughter, through puncture of the cerebellomedullary cistern using sterile 10 cc disposable syringes. Samples were processed within 2 hrs after collection for measurement of glucose level and the rest were stored at -20°C bending analysis.

2. Blood collection

Blood samples were collected from the jugular vein in plain vacutainers. Blood for determination of serum glucose concentration was collected in vials containing sodium fluoride. Serum was harvested by centrifugation of the blood at 2500 rpm for 15 minutes.Non-hemolyzed clear serum sampleswere stored at -20°C bending analysis.

3.Laboratory Analysis

Color and consistency of CSF were tested visually.    

Serum and CSF concentration of total protein (TP), albumin (Alb), glucose, Creatinine, Urea, Mg , Ca, and the activity of the enzymes Alanine Amino Transferase (ALT), Alkaline Phosphatase (ALP), and Aspartate Amino Transferase (AST) were determined by colorimetric method, using commercial kits(Linear Chemicals Ltd.- Spain ), following the procedures set by the manufacturer. Na and K were measured by a flame photometer (Corning 400, England),        

Statistical analysis:

          The data were presented as means, standard error of the means (SEM) and range values. Comparison between the means was performed by student's t-test as described by Gomez and Gomez, (1984).    

Results

No pathological changes were seen at the postmortem examination in the animals from which blood and CSF were obtained. Cerebrospinal fluid was watery, clear and colorless. Mean (+SEM) and range of the studied parameters in CSF and serum samples are presented in Tables (1 and 2).

          Total proteins and albumin concentrations in serum were significantly higher (P<0.01) than in the CSF. Urea, creatinine and glucose concentrations in CSF were insignificantly lower than in serum. The mean Ca, K, and Na concentrations in CSF weresignificantly lower than in serum, (P<0.05), while there was a non-signiicant increase in the level of Mg in the CSF than in the serum . The activities of the enzymes ALT, AST and ALP were significantly higher (P<0.05) in serum than in CSF.

 

 

 

 

 

 

 

 

 

 

 

 

 

Table  (1). Means +SEM and ranges of Non-electrolytes, in CSF and Serum of Sudanese Cattle (No=30)

Significance

level

Serum Mean±SEM+ ranges

CSF   Mean±SEM+ ranges

Parameters

HS

7920±0.03

7700-8400

6.45±0.02

6.10-6.70

Total proteins  mg/100ml

HS

3920±0.03

3700-4300

2.57±0.03

2.30-2.80

Albumin mg/100ml

NS

27.27±0.26

25.00-30.00

17. 97±0.25

16.00-20.00

Urea  mg/100ml

NS

1. 36±0.02

1.20-1.60

1.17 ±0.02

1.00-1.40

Creatinine  mg/100ml

NS

48.18±0.28

46.00-51.00

47.67±0.26

45.00-51.00

Glucose  mg/100ml

 

HS: Sig. at P<0.01

NS: Not Sig.

 

 

 

 

 

 

 

 

 

 

Table  (2). Mean +SEM and ranges of macro minerals and enzymes activity in CSF and Serum of Sudanese Cattle (No=30).

Significance

level

Serum  Mean±SEM+Ranges

CSF   Mean±SEM+ranges

Parameters

S

7. 72±0.02

7.50-7.90

5.48±0.03

5.10-5.80

Ca   mg/100ml

NS

1.28±0.02

1.10-1.50

1.49±0.03

1.25-1.80

Mg  mg/100ml

S

3. 66±0.03

3.20-3.90

3.09±0.03

2.90-3.30

K   mmol/L

S

113.20±0.99

103.00-121.00

104.87±1. 57

89.00-122.00

 Na  mmol/L

S

30.73±0.61

20.00-35.00

20.13±0.37

16.00-24.00

AST U/L

S

10.17±0.44

1.00-14.00

5.50±0.18

4.00-7.00

ALT U /L

S

84.08±0.29

81.00-87.00

 

75.10 ±0.51

70.00-79.00

ALP  U /L

           

S: Sig. at P<0.05

NS: Not Sig.

 

Discussion

          CSF proteins are determined as an index of the integrityof the blood-brainbarrier. In the present study CSF concentrations of TP was lower than those of serum, and this seems to agree with the finding of Hiroshi and Miyuki, (2001). The mean TP value in CSF reported here is within the range of Scott (1990) ; and are far lower than the values given for calves (St Jean et al., 1997) and for adult cows (Soliman and El Amrousi, 2010 ). The present TP values are comparable with  those reported in Sudanese camel, (Ahmed et al., 2009); and are higher than that found  in adult llamas (Welles et al., 1994) Iranian dromedary camels (Nazifi and Maleki., 1998 .) sheep (Ameri and Mousavian ., 2007) and rabbits ( Jass et al. 2008). CSF protein concentrations may vary with age and site of collection. In, horses (Rossdale, et al,1982), cattle (Stocker et al., 2002) and camels(Al-Sagair et al. 2005) CSF protein concentrations was observed to vary with age. Higher protein levels were also reported in lumbosacral CSF when compared to atlantooccipital CSF, (Andrews et al, 1994). 

The CSF Creatinine, and urea, concentration reported are insignificantly lower than those in serum, and this accord with the finding of Hiroshi and Miyuki, (2001) in cattle. The mean urea concentration in CSF obtained in this study is higher than those reported for Holstein calves (St Jean et al. 1997) and is comparable with the values obtained for sheep and goats (Kaneko, 1997). In the present study CSF creatinine concentration is higher than the given values for Iranian camels (Nazifi and Maleki, 1998) and Sudanese camels (Ahmed et al., 2009).

The CSF glucose concentration reported for the Sudanese cattle in this study is higher than the findings of Welles et al., (1992) in dairy and beef cattle ,and (Ahmed, et al., 2009)  in Sudanese camels . Higher CSF glucose values than of the current work are reported in Holstein calves (St Jean et al., 1997) , camels (Al-Sagair et al. 2005); and sheep (Ameri and Mousavian, 2007) , this may be due to age and breed difference. Kaneko et al. (1997) reported that the concentration of CSF glucose depends upon the blood glucose concentration, the rate of glucose transport into the CSF, and the metabolic rate of the central nervous system; so this may explain the variation in the CSF glucose concentration between the present work and the other studies.

In this study, most serum electrolytes levels are higher than CSF electrolytes concentration. The level of some CSF electrolytes   concentration is determinedin view of their importance for diagnosis of salt poisoning and for assessment of fluid therapy (Welles et al., 1992) .Sodium and calcium are particularly importantin the establishment of the thermal set point in the hypothalamus(Myers and Veale, 1970). K  and Na concentration in CSF are lower than their corresponding  values in serum which is in line with other reports (Welles, et al., 1992; Duncan, et al., 1994; Jean, et al., 1997;Ahmed ,et al., 2009).However, the CSF concentration of K, Na, and Ca in this study is comparable to the value reported in adult cattle (, Fankhauser, 1962; Welles et al. , 1992), buffaloes (Khadjeh  et al., 2005)  but higher than those reported for horse, sheep and goat (Kaneko, 1989). The CSF magnesium concentration in this study is higher than that in serum and this agrees with the finding of Khadjeh et al. (2005).   Comparable CSF magnesium mean values to the current work were obtained in buffaloes (Khadjeh et al. 2005), and higher values were reported in cows, horses and sheep (Kaneko, 1989).The activities of the enzymes (ALP, ALT, AST) in the CSF are lower than those of the serum which is in the line with the observation of Ahmed et al., (2009) in Sudanese camels; but are much higher than those reported in Iranian camels (Nazifi and Malek, 1998).

The variations observed in the values obtained in this study when compared with those of other researchers can be attributed to differences in animal breed, age, species (Stocker et al., 2000).development of the brain blood barrier, site of sampling, time of analysis after sampling, storage conditions (Andrews et al. 1994 and Fry et al., 2006), and or techniques used for biochemical analysis.

The present results may be used, together with other similar findings as reference values for serum and CSF constituents in Sudanese cattle. 

Acknowledgment

This work was kindly financed by The Scientific Research Council, Sudan University of Science and Technology.                     

References

Ahmed, S. H; Shadia. A.O; and Gameel, AA. (2009). Some Normal Constituents in Serum and Cerebrospinal Fluid in Sudanese Camels. Assiut Vet. Med. J. Vol. 55:163-170.

Al-Sagair ,O. A.; Fathalla, S. I and Abdel-Rahman, H. A.(2005) .Reference values and age related changes in cerebrospinal fluid and blood components in the clinically normal male Dromedary camel. J. of Animal and Vet. Advances 4:467-469.

Ameri, M. and Mousavian, R. (2007). Analysis of cerebrospinal fluid from clinically healthy Iranian fat-tailed sheep  Vet.Rese. Com.,31:77-81.

Aminlari, M. and Mehran, M. M. (1988). Biochemical properties of cerebrospinal fluid of sheep and goats comparison with blood. Journal of Veterinary Medicine, 35: 315-319.

Andrews, F.M.; Geiser, D. R. and Somardah, C. S.(1994). Albumin quotient, IgG concentration and IgG index determination in cerebrospinal fluid of neonatal foals. Am. J. Vet. Res. 55: 741-745.

Braun, V.; Gerspach,G.; Salis, F.; Flege, K. (2003). Clinical finding in four cattle with abscesses in cervical vertebrae. Schureiz Arch Trerheiked.145:124-128.

Di Terlizzi, R. and Platt, S. R. (2008). The function, composition and analysis of cerebrospinal fluid in companion animals: Part II-Analysis. Vet. J. 180:15-32.

Fankhauser, R. (1962). The cerebrospinal fluid, In: Innes JRM, Saunders LZ, 1st ed. Comparative Neuropathology. Academic Press,London,pp21-54.

Fry, M. M.; Vernau, W; Kass, P. H. and Vernau, K. M. (2006). Effects of time, initial composition, and stabilizing agents on the results of canine cerebrospinal fluid analysis Vet. Clin. Pathol. 35: 72-77.

Garma-Avina, A. and Tyler, J. W. (1999). Large granular lymphocyte   pleocytosis in the cerebrospinal fluid of a dog with necrotizing meningoencephalitis, J. Comp. Pathol. 121: 83-87.

Gomez, K. A. and Gomez, A.A. (1984). Statistical Procedure for Agricultural Research, 2nded. Willy and Sons Inc.

Hiroshi, S.; and Miyuki, I. (2001). Concentrations of Glucose, Nitrogenous Metabolites and Minerals in the Cerebrospinal Fluid (CSF) and Blood Plasma of Cattle Anim. Sci. J. Vol.72:557-563.  

Jass, A.; Matiasek, K.; Henke, J.; Kuchenhoff, H.; Hartmann, K.; and Fischer, A. (2008). Analysis of cerebrospinal fluid in healthy rabbits and rabbits with clinically suspected encephalitozoonosis. The Veterinary Record, 162: 618-622.

Kaneko, J. J.; Harvey, J. W. and Bruss, M. L.(1997). Clinical Biochemistry of Domestic  Animals 5th Ed.  Pub. Academic Press  USA. pp :904.

Khadjeh, G. H; Razijalali,M.; Rajekh, R.; and Sayahi, N (2005).Normal electrolytes value in Cerebrospinal  fluid and Serum in the Iranian Buffaloes. Iranian J. of Vet. Res. Vol. 6: 21-27.

Myers, R. D.; and Veale, W.L. (1970). Body temperature: possible ionic mechanism in the hypothalamus controlling the set-point. Science 170: 95-97.

Nazifi, S. and Maleki, K. (1998).Biochemical analysis of serum and cerebrospinal fluid in clinically normal adult camels (Camelus romedaries) Research in Veterinary Science 65:83-84.

Rossadale, P. D.; Cash, R. S.G. and Leadon, D. P. (1982). Biochemical constituents of cerebrospinal fluid in premature and full term foals. Equine Vet. J. 14: 134-138.

Scott,PR; Aldridge,P.M.; Clarke,M; and Will,R.G.(1990).Cerebrospinal fluid studies in normal cows and cases of bovine spongiform encephalopathy.  Br.Vet. J. 146:88-90.  

Sofaly, C. D.; Read, S. M.; Garden, J.G.; Dubey, J. P.; Ogleebace, C. G., Njoku, D.L.; and Savill, W. J. (2000).Experimental induction of protozoan of equine myeloencephalitis (EPM) in horses, Effect of sarcocytosis neuron sparocyst inclution dose on the development of clinical neurological disease. Parasitol. 88:1164-1170.

Soliman, M.K. and El Amrousi,S .(1965).Some studies on the cerebrospinal fluid of healthy cattle. Zentrlblatt fur Veterinamedizin Reihe A  12: 769-776.

St Jean, G.; Yvorchuk, S. K.; Anderson, D. E.; and Moore, W. E. (1997). Cerebrospinal fluid constituents collected at the atlanto-occipital site of xylazine hydrochloride sedated, healthy 8- week old Holstein calves Can. J. Vet. Res. 61:108-112.

Stocker, H.; Sicher, D.; Rusch; P. and Lutz, H. (2002) .Reference values in the cerebrospinal fluid of calves between four and eight weeks of age, Schweiz Arch Tierheilkd 44:283-288.

Stokol, T.; Divers, T. J.; Arrigan, J. W.; and McDonough, S. P. (2009). Cerebrospinal fluid finding in cattle with central nervous system disorders:a retrospective  study  of 102 cases  (1990-2008), Vet. Clin. Pathol. 38:103-112.

Tyler, J.W.; Wells, E.G.;and Sorjonen, D.G. (1993). Cerebrospinal fluid composition of cattle with endotoxin-induced mastitis treated with isotonic (0.9%) or hypertonic (7.5%) sodium chloride. J. Vet. Intern. Med. 7: 91-94.

Welles, E. G.; Pugh, D. C.;and Wenzel, G.W. (1994). Composition of cerebrospinal fluid in healthy adult llamas. Am. J. Vet. Res.  55: 1075-1079.

Welles, E. G.; Tyler, J. W.; Sorjonen, D.C. and Whatley, E. M. (1992). Cerebrospinal fluid composition in clinically normal adult cattle Am. J. Vet. Res. 53: 2050-7.

References
Ahmed, S. H; Shadia. A.O; and Gameel, AA. (2009). Some Normal Constituents in Serum and Cerebrospinal Fluid in Sudanese Camels. Assiut Vet. Med. J. Vol. 55:163-170.
Al-Sagair ,O. A.; Fathalla, S. I and Abdel-Rahman, H. A.(2005) .Reference values and age related changes in cerebrospinal fluid and blood components in the clinically normal male Dromedary camel. J. of Animal and Vet. Advances 4:467-469.
Ameri, M. and Mousavian, R. (2007). Analysis of cerebrospinal fluid from clinically healthy Iranian fat-tailed sheep  Vet.Rese. Com.,31:77-81.
Aminlari, M. and Mehran, M. M. (1988). Biochemical properties of cerebrospinal fluid of sheep and goats comparison with blood. Journal of Veterinary Medicine, 35: 315-319.
Andrews, F.M.; Geiser, D. R. and Somardah, C. S.(1994). Albumin quotient, IgG concentration and IgG index determination in cerebrospinal fluid of neonatal foals. Am. J. Vet. Res. 55: 741-745.
Braun, V.; Gerspach,G.; Salis, F.; Flege, K. (2003). Clinical finding in four cattle with abscesses in cervical vertebrae. Schureiz Arch Trerheiked.145:124-128.
Di Terlizzi, R. and Platt, S. R. (2008). The function, composition and analysis of cerebrospinal fluid in companion animals: Part II-Analysis. Vet. J. 180:15-32.
Fankhauser, R. (1962). The cerebrospinal fluid, In: Innes JRM, Saunders LZ, 1st ed. Comparative Neuropathology. Academic Press,London,pp21-54.
Fry, M. M.; Vernau, W; Kass, P. H. and Vernau, K. M. (2006). Effects of time, initial composition, and stabilizing agents on the results of canine cerebrospinal fluid analysis Vet. Clin. Pathol. 35: 72-77.
Garma-Avina, A. and Tyler, J. W. (1999). Large granular lymphocyte   pleocytosis in the cerebrospinal fluid of a dog with necrotizing meningoencephalitis, J. Comp. Pathol. 121: 83-87.
Gomez, K. A. and Gomez, A.A. (1984). Statistical Procedure for Agricultural Research, 2nded. Willy and Sons Inc.
Hiroshi, S.; and Miyuki, I. (2001). Concentrations of Glucose, Nitrogenous Metabolites and Minerals in the Cerebrospinal Fluid (CSF) and Blood Plasma of Cattle Anim. Sci. J. Vol.72:557-563.  
Jass, A.; Matiasek, K.; Henke, J.; Kuchenhoff, H.; Hartmann, K.; and Fischer, A. (2008). Analysis of cerebrospinal fluid in healthy rabbits and rabbits with clinically suspected encephalitozoonosis. The Veterinary Record, 162: 618-622.
Kaneko, J. J.; Harvey, J. W. and Bruss, M. L.(1997). Clinical Biochemistry of Domestic  Animals 5th Ed.  Pub. Academic Press  USA. pp :904.
Khadjeh, G. H; Razijalali,M.; Rajekh, R.; and Sayahi, N (2005).Normal electrolytes value in Cerebrospinal  fluid and Serum in the Iranian Buffaloes. Iranian J. of Vet. Res. Vol. 6: 21-27.
Myers, R. D.; and Veale, W.L. (1970). Body temperature: possible ionic mechanism in the hypothalamus controlling the set-point. Science 170: 95-97.
Nazifi, S. and Maleki, K. (1998).Biochemical analysis of serum and cerebrospinal fluid in clinically normal adult camels (Camelus romedaries) Research in Veterinary Science 65:83-84.
Rossadale, P. D.; Cash, R. S.G. and Leadon, D. P. (1982). Biochemical constituents of cerebrospinal fluid in premature and full term foals. Equine Vet. J. 14: 134-138.
Scott,PR; Aldridge,P.M.; Clarke,M; and Will,R.G.(1990).Cerebrospinal fluid studies in normal cows and cases of bovine spongiform encephalopathy.  Br.Vet. J. 146:88-90.  
Sofaly, C. D.; Read, S. M.; Garden, J.G.; Dubey, J. P.; Ogleebace, C. G., Njoku, D.L.; and Savill, W. J. (2000).Experimental induction of protozoan of equine myeloencephalitis (EPM) in horses, Effect of sarcocytosis neuron sparocyst inclution dose on the development of clinical neurological disease. Parasitol. 88:1164-1170.
Soliman, M.K. and El Amrousi,S .(1965).Some studies on the cerebrospinal fluid of healthy cattle. Zentrlblatt fur Veterinamedizin Reihe A  12: 769-776.
St Jean, G.; Yvorchuk, S. K.; Anderson, D. E.; and Moore, W. E. (1997). Cerebrospinal fluid constituents collected at the atlanto-occipital site of xylazine hydrochloride sedated, healthy 8- week old Holstein calves Can. J. Vet. Res. 61:108-112.
Stocker, H.; Sicher, D.; Rusch; P. and Lutz, H. (2002) .Reference values in the cerebrospinal fluid of calves between four and eight weeks of age, Schweiz Arch Tierheilkd 44:283-288.
Stokol, T.; Divers, T. J.; Arrigan, J. W.; and McDonough, S. P. (2009). Cerebrospinal fluid finding in cattle with central nervous system disorders:a retrospective  study  of 102 cases  (1990-2008), Vet. Clin. Pathol. 38:103-112.
Tyler, J.W.; Wells, E.G.;and Sorjonen, D.G. (1993). Cerebrospinal fluid composition of cattle with endotoxin-induced mastitis treated with isotonic (0.9%) or hypertonic (7.5%) sodium chloride. J. Vet. Intern. Med. 7: 91-94.
Welles, E. G.; Pugh, D. C.;and Wenzel, G.W. (1994). Composition of cerebrospinal fluid in healthy adult llamas. Am. J. Vet. Res.  55: 1075-1079.
Welles, E. G.; Tyler, J. W.; Sorjonen, D.C. and Whatley, E. M. (1992). Cerebrospinal fluid composition in clinically normal adult cattle Am. J. Vet. Res. 53: 2050-7.