Introduction

Recent years have seen a dramatic increase in the numbers of American bison (Bison bison) raised commercially. As commercial bison production grows, new information is needed on all aspects of production including disease syndromes seen in this species. Critical to the need to assess disease in bison is the need for normal parameters, particularly serum chemistries and hematological values. The few documented previous studies often include low numbers of animals, semi-wild populations, or address specialized groups. There was a need, therefore, for a study evaluating baseline clinical chemistry and hematology values in a large number of American bison. This work is an attempt to produce reliable normal values against which diseased samples can be compared for therapeutic purposes.

Materials and Methods

Blood samples were collected during the months of October 1998 thru March 1999, and October 1999 thru March 2000. A convenience sample of 13 herds in eleven states (MN, IN, CO, WY, SD, NC, WI, NM, NE, MT, KS) was selected. Herd selection was based on bison raised in a production setting, voluntary participation in the study, all expenses in collecting the sample by a licensed veterinarian were borne by the participating herd, the bison in these herds were apparently healthy and each herd was located close enough to a national express shipping company to ensure samples could be collected and sent overnight to participating laboratories.

A convenience sample of approximately 30 bison per herd was selected: 10 animals from 0 to 12 months of age, 10 animals from 13 to 24 months of age, and 10 animals over 24 months of age. Bison were physically restrained with a squeeze chute. No tranquilizers or sedatives were used. Four tubes of jugular blood were collected from each animal: one royal blue top, one red top, and two purple tops. ID number, age and sex were recorded for each animal. A minimum of 3 ml of blood was collected in each of the Royal Blue Top and the Red Top tubes. A minimum of 1 ml of blood was collected in each of the Purple Tops. The Royal Blue Top and Red Top tubes were allowed to set at room temperature. The Purple Top tubes were inverted at least 8 times to ensure adequate mixing with the anticoagulant and kept cool.

Locally, the Royal Blue Top and Red Top tubes were spun in a centrifuge to separate the plasma and sera, respectively. Plasma and sera was then transferred to snap top (FalconÒ) tubes for shipping. All tubes were sent via overnight delivery to respective laboratories on ice. Differential counts were done manually on Diff-Quik stained slides by a single operator. Data was collated and analyzed using Epi-Info software.

Results

A total of 406 blood samples were collected during the months of October thru March. The results are categorized in Table 1.

 

Table 1. North Dakota State University Survey of Complete Blood Counts, Serum Chemistries, and Serum Electrolytes for Bison from 13 herds in 11 States, 1998-2000.

 

 

 

Test

 

 

 

Units

 

 

 

n

 

 

 

Mean

 

 

 

Std Dev

 

95%

Confidence Interval

NDSU

Reference Values for Cattle

WBC

x 103/Fl

320

4.968

1.936

1.1 – 8.8

4.0 – 12.0

Monos

x 103/Fl

320

0.163

0.149

0 – 0.5

0 – 0.9

Lymph

x 103/Fl

320

2.167

0.992

0.2 – 4.2

2.5 – 7.5

Segs

x 103/Fl

320

2.395

1.413

0 – 5.2

0.6 – 4.0

Bands

x 103/Fl

320

0.049

0.122

0 – 0.3

0 – 0.1

Eos

x 103/Fl

320

0.192

0.223

0 – 0.7

0 – 2.4

Baso

x 103/Fl

320

0.001

0.006

0 – 0.01

0 – 0.2

RBC

x 106/Fl

361

9.375

1.270

6.8 – 11.9

5.0 – 8.0

Hgb

g/dl

361

17.764

1.532

14.7 – 20.8

8.0 – 14.0

HCT

%

361

49.934

4.588

40.8 – 59.1

26.0 – 42.0

MCV

fl

361

53.773

5.595

42.6 – 65.0

37.0 – 54.0

MCH

pg

361

19.135

1.943

15.2 – 23.0

 

MCHC

%

361

35.611

1.092

33.4 – 37.8

26.0 – 36.0

RDW

%

361

24.016

3.038

17.9 – 30.1

 

PLT

x 103/Fl

361

297.535

126.845

43.8 – 551.2

175.0 – 620.0

Glucose

mg/dl

406

122.623

42.936

36.8 – 208.5

45.0 – 75.0

BUN

mg/dl

406

15.879

6.497

2.9 – 28.9

20.0 – 30.0

Creatinine

mg/dl

406

2.573

0.494

1.6 – 3.6

1.0 – 2.0

T Protein

g/dl

405

8.181

1.096

6.0 – 10.4

6.7 – 7.5

Albumin

g/dl

405

4.182

1.093

2.0 – 6.4

3.0 – 3.5

GGTP

U/L

236

23.941

10.854

2.2 – 45.6

6.0 – 17.4

AlkPhosph

U/L

167

51.683

20.873

9.9 – 93.4

0.0 – 488.0

Calcium

ppm

360

97.699

7.229

83.2 – 112.2

85 – 110

Copper

ppm

360

0.789

0.249

0.29 – 1.29

0.65 – 1.50

Iron

ppm

360

1.486

0.439

0.61 – 2.36

1.30 – 2.50

Magnesium

ppm

360

21.098

2.813

15.5 – 26.7

20 – 35

Phosphorous

ppm

360

62.176

17.116

27.9 – 96.4

45 – 80

Zinc

ppm

360

10.18

0.252

0.51 – 1.52

0.80 – 1.40

Sodium

ppm

360

3327

141.753

3043 – 3611

2900 – 3450

Potassium

ppm

360

224.878

47.722

129 – 320

156 – 226

SE none

ng/ml

157

60.497

11.890

37 – 84

 

SE supp

ng/ml

208

239.803

72.685

94 – 385

 

SE toxic

ng/ml

30

623.267

132.804

358 – 889

 

Selenium

ng/ml

395

197.658

162.347

0 – 522

120 – 200

 

White cell parameters

The range for total white cell numbers was shifted lower for bison as compared to cattle. Lymphocyte and monocyte numbers were shifted in the same direction as well. However, the range for granulocytes (neutrophils, bands, eosinophils and basophils) was expanded creating a higher end point than that seen for cattle.

Red cell parameters

Red cell indices were somewhat higher (2.0 x 106/ml) in bison as compared to cattle. Additionally, hemoglobin concentrations in bison were appreciably elevated over cattle values, as was hematocrit. Finally, although bison and cattle ranges overlapped in the middle, bison platelet numbers were shifted lower than cattle.

Serum chemistry

Glucose, albumin, serum protein and GGTP had similar but somewhat wider ranges than bovine values. Both BUN and creatinine were slightly elevated above bovine levels.

 

Minerals

Calcium, iron, magnesium, phosphorus, zinc, sodium and potassium correlate well with bovine reference values used at the NDSU-VDL. Copper is slightly lower in bison than in cattle. Selenium had a very wide reference range. For a more complete comparison, selenium was stratified by the non-use/use of selenium supplementation and for one group of bison grazing on selenium pastures toxic to cattle. These results are in Table 1. In this study, bison not supplemented for selenium had very low selenium levels. Bison on some type of selenium supplementation had selenium levels very comparable with normal bovine levels. Bison grazing selenium toxic pastures had very high selenium levels, yet no adverse health conditions were reported.

 

Discussion

The results of this study provide veterinarians and other bison health workers with usable clinical blood values. Blood values that correlate well with previous studies are HCT, Hb, Creat, and BUN (Miller89, Marler75 and Wallach83). The bison in this study had lower WBC parameters than in previous studies (Miller89, Marler75, and Azugg93). The reason for this finding is unknown. As noted in previous studies many environmental factors can cause variation in hematologic and blood chemistries (Franzmann71, Pederson75). Also, one previous study included actively infected animals in the results (Miller89), one study included animals shot with a high powered rifles (Zaugg93) and others were taken from animals on free range or received very little managed care (Marler75 and Mehrer76). The bison in these herds were from managed production units and utilized humane handling techniques to collect the samples. A plausible explanation for the lower WBC levels is that these bison were on a higher plane of health care because producers equate health animals with higher profitability. Also, these herds could have self-selected for higher health status because of the selection criteria.

This is the first study to report selenium levels in bison. Furthermore, this is the first study to stratify bison selenium levels by use or non-use of selenium supplementation and the effect of grazing selenium toxic pastures. These levels would suggest that bison have a much higher tolerance level for selenium than cattle, and they may even have a higher requirement for selenium in their diet. More research is needed in this area.

 

References

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Marler RJ. Some hematologic and blood chemistry values in two herds of American bison in Kansas. J Wildl Dis 11:97-100, 1975

Mehrer CF. Some hematologic values of bison form five areas of the United States. J Wildl Dis 12:7-13, 1976

Miller LD, Thoen CO, Throlson KJ, Himes EM, Morgan RJ. Serum biochemical and hematologic values of normal and Mycobacterium bovis-infected American bison. J Vet Diagn Invest 1:219-222, 1989.

Vestweber JG, Johnson DE, Merrill GL, Staats JJ. Hematological and blood chemistry profiles of American bison grazing on Konza prairie of Kansas. J Wildl Dis 27:417-420, 1991.

Zaugg JL, Taylor SK, Anderson BC, Hunter DL, Ryder J, Divine M. Hematologic, serologic values, histopathologic and fecal evaluations of bison from Yellowstone park. J Wildl Dis 29:453-457, 1993.

Sikarskie JG, Schillhorn van Veen TW, van Selm G, Kock MD. Comparative blood characteristics of ranched and free-ranging American bison (Bison bison). Am J Vet Res 51:955-957, 1990.

Clemens ET, Meyer KL, Carlson MP, Schneider NR. Hematology, blood chemistry and selenium values of captive pronghorn antelope, white-tailed deer and American bison. Comp Biochem Physiol C 87:167-170, 1987.

Hawley AW, Peden DG. Effects of ration, season and handling on composition of bison and cattle blood. J Wildl Dis 18:321-338, 1982.

Haines H, Chichester HG, Landreth HF Jr. Blood respiratory properties of Bison bison. Respir Physiol 30:305-310, 1977.