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Haematological Values for the Clinically Normal Bull
Br. vet. ] . (1g66),
122,
239
HAEMATOLOGICAL VALUES FOR THE CLINICALLY NORMAL BULL By R. H. C. PENNY and A. M. ScoFIELD, Department of Veterinary Medicine, University of Bristol,
and H. CEMBROWICZ, Horlicks Farms and Dairies Limited, Ilminster
SUMMARY The blood picture of 152 bulls standing at artificial insemination centres is described. The data obtained were analysed by breed and by age, and significant between-breed and age differences were found . The advantage of using absolute values for the differential white blood cell count is emphasized.
A number of workers have studied individual aspects of the blood picture of the bull (e.g. Fraser, I930; Scarborough, I93I; McCay, I93I), but no detailed study has been made. Holman (I955) has criticized comparisons made between cows and bulls because of differences in their environmental conditions. In I g62 approximately I ,ooo bulls were being kept in insemination centres (Federation of U.K. Milk Marketing Boards, I963). This paper describes the blood picture of such bulls. MATERIALS AND METHODS General All the I 52 clinically normal bulls examined were "standing" at local insemination centres, and blood samples were collected over a two-year period. The jugular vein was used for sampling and the dipotassium salt of Sequestrene (ethylenediaminetetra-acetic acid) was used as an anticoagulant in all cases. All the bleedings were performed in the morning.
Haematological estimations The red cell count (RBC), packed cell volume (PCV), haemoglobin estimation (Hb), reticulocyte count, Heinz body count, total white cell count (WBC) and differential WBC were determined by techniques previously described (Penny, Wright & Stoker, I964; Penny, David & Wright, I964). The mean corpuscular volume (MCV), the mean corpuscular haemoglobin concentration (MCHC) and absolute values for the differential WBC were calculated.
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TABLE
II
NORMAL HAEMATOLOG1CAL VALU ES FOR TilE BULL
Breed No . of bulls RBC (106{cu. m:m. ) Hb (g. % ) PCV (%) [I & 2] MCV (cu. J.l) MCHC (% ) (Io 3fcu.
WBC < 2 years
mm.) [2]
> 2 years Dijferential leucocyte count: [3] Neutrophils (%) (1o 3{cu. mm. ) Lymphocytes (%) (1oS{cu. mm.) Monocytes (% ) (per cu. mm. ) Eosinophils (% ) (per cu. mm. )
Friesian
Hereford
Slwrthorn
Charolais
Guernsry
Ayrshire
All breeds
74
9
16
5
28
20
I 52
7"43± I·26 I3"9 ± I·go 43"3 ± 2·58(37) s6·1± 9"24 33"7± 5"02
7"45± I·o6 I3"3± I·s8 38·o(2) 48·6± 6·g3 38·o± 2"34
6·8o± I"04 13"9 ± I·67 42 "2± 5"49(7) 6I ·6± I3·48 32·6± 4·g8
g·Bo ± 3·s6(I I) s ·8s ± 2"45(63 )
g·ss(2)
-
43"2± 8·8g(26) 2•44 ± 1"31 (26) 39"9± 8·53 (26) 2·18± o·g2(26) 4"83± 4"22 311±271 10"4;:!: s·8o(26 ) 590±354 (26)
9"22 ± I•77(7)
-
3"50± 1"94 384 ± 223
-
-
s ·Bg± 1"47{I6) 32"9± 6·66(g) ! •8!± 0"52 (9) so·8 ± 6·25(9) 2·83 ± 0·73(9) 3"13± 3"4 1 342±245 g·78± 2·6o(g) s67±2s8 (g)
Significance
7"51 ± I·25 I3·I± I•53
-
s6·2± I2·8 5 33"3± 6·75
6·62± o·go 12"9± I"93 40"2± 3"79(I2) 58·8± 7"65 33"2± 3·66
7"52 ± I"35{3 ) 4"75(2)
7•8o ± 2"25(6) 5"91± I ·34(22)
-
33"2± 9"24(10) I·8g± 0"97(10) 47"0± 8·41(10) 2"29± o·gg(10 ) 6·o2± 5"53 290±217 13·0 ± 8·76(10) 57I±257 (10)
-
s ·IO ± 5"02 253±225
-
-
6·92± o·92 I3·s± 2"3I 45"I± 5"12(5) 57"4± 7·8s 3I·g± 3"00 7·65 ± 2"I3(5) 6·IS ± 2"3I(IS ) 3I ·6± 10·8(g) 1·8o ± 1·05(9) 55" 1± g·s8 (g) 3"07± 1"25(9) 3"75± 3"26 204±194 8·33± 4"97(9) 492 ± 341 (g)
The values quoted are means and standard deviations. [1] Means quoted for 3 to 8-year age group only. *=P< o·os [2] Figures in brackets denote the number of animals sampled in each group. ** = P < o·oi [3] Means of the differential count for neutrophils, lymphocytes and eosinophils for bulls 8 years and over.
7"I4 ± I"I3 I3"4 ± I·94 42"7± 3·68(63) s6·g± g·68 33"5 ± 5·og 8·68 ± 2"94(27) 6·o8 ± I·gi(I25 ) 37"7 ± 9"14(54) 2·00± o·g6(54) 4s-6 ± 8·64(54) 2•46 ± 1"02(54) 4·o6 ± 4"20 299±250 1o·s± 6·23(54) s66±313 (54)
NS = Not significant.
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BRITISH VETERINARY JOURNAL, 122, 6
Statistical methods The data for Friesian bulls were first selected and divided into the following age groups: under two years, yearly thereafter up to ten years, and animals over ten years of age. The data .were examined graphically and, where trends were suggested, the material was submitted to an analysis of variance (the variances being assumed the same) or, where linear trends seemed likely, by regression analysis. Where age differences were detected the significant means were identified using the standard error of the mean method, and comparisons between breeds were made using the homogeneous ranges of the data which were determined from the graphs, and verified by statistical analysis. Where no age differences occurred, all the data for the other breeds were used in the calculation of means and standard deviations. Between-breed differences were tested by analysis of variance. The null hypothesis was rejected at and below the 5 per cent level of probability (P < o·os). Means and standard deviations are quoted in the text. RESULTS
Red cell count From a graph of the RBC for the 74 Friesians (Table I), a slight increase with age was suspected. However, regression analysis of these data gave a change of o·o82 million/cu. mm./year, which was not significant. Analysis of variance of the data failed to show any significant age differences. Between-breed analysis of the data from all age groups (Table II) showed the RBC of Guernsey bulls to be significantly lower than that of Friesians (P < o·or). There were. no signific~nt differences between the other breeds. Packed cell volume Analysis of the data for PCV presented in Table I revealed significant differences between the age groups (P
Age Group Breed
Friesian Hereford Shorthorn Guernsey Ayrshire
No. of bulls
< 3years
PCV %
No . of bulls
16 . 7
36·7 ± 4'23 34'4± 2·96 35'0 36'3±2"44 36'4± 3'41
37 2 7 12 5
9 7
All breeds 36·1 ± 3·56 63 40 The values quoted are means and standard deviations.
3-8years
No. of bulls
9years +
43'3±2·58 38·o 42 '2±5'49 40'2±3'79 45'1±5' 12
21
39' 7±2 '92
8 7 8
45'7 ± 4'87 38·9 ± 4'76 41'3 ± 4'55
42' 7± 3·68
44
41 '0±4' 79
PCV %
PCV %
HAEMATOLOGICAL VALUES FOR THE BULL
243
three to eight years in both Guernseys (P
Haemoglobin No significant differences between the age groups in Friesians were demonstrated, although the trend followed that of the PCV (Table I). There were no significant differences between breeds (Table II). Reticulocytes and Heinz bodies Reticulocytes were present in three bulls and ranged from o·o2 to o·6I per cent. Heinz bodies were present in four bulls and the range was o·o2 to 0·36 per cent. Mean corpuscular volume No significant differences between the age groups in Friesians were shown, although the trend followed that of the PCV. Herefords had a significantly lower MCV (Table II) than the other breeds (P
BRITISH VETERINARY JOURNAL,
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and older (Table II) showed Friesians to have a higher percentage of neutrophils than the other breeds (P < o·os). However, analysis of the absolute values did not show a significant breed difference for this period. qmphocytes. Distribution of the data for Friesians indicated a decrease in the percentage of lymphocytes up to seven years of age, after which the count remained relatively stable (Fig. 1 ). When the absolute count was plotted it
65 - 6,000
u
50
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45
2 0 ~
40
20
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2
4
3
5
6
7
8
9
10
>10
Age (years)
Fig.
1.
Changes with age in the lymphocyte and lobulated neutrophil counts of Friesian bulls. = % lobulated neutrophils 0 0 = absolute number of lobulated neutrophils/cu. mm.
e •
e
-
- - -
•
0 - - - - 0
=
% lymphocytes
=
absolute number of lymphocytes/cu. mm.
revealed a more pronounced decrease than the percentages alone suggested. Regression analysis of the percentage oflymphocytes with age gave a coefficient of -4·1 per cent/year ±o·6g, which was highly significant (P < o·or). Regression using the absolute values showed the decrease in lymphocyte numbers with age for this period to be highly significant (b = o·62 x ro 3 fcu. mm.fyear ±o·r2; P
HAEMATOLOGICAL VALUES FOR THE BULL
245
centages or absolute values were detected and there were no breed differences when all the data were used. Eosinophils. Distribution of the data for Friesians indicated that the percentage of eosinophils increased up to seven years of age, after which no regular increase could be seen. Regression analysis of the percentage of eosinophils with age gave a coefficientofo·72 percent/year ±0·38, which was not quite significant at the 5 per cent level. The absolute values did not show a trend wi~h age. There was a significant correlation between the percentages of eosinophils and lymphocytes at all ages (r = 0·54; P < o·oi). In view of this correlation, and the similarity in the shape of graphs of the percentage of eosinophils and neutrophils with age, the breed means were calculated from the bulls of eight years and older. Analysis of these data failed to reveal any significant breed differences in either percentages or absolute values (Table II). Basophils. These were present in 19·7 per cent of animals, with a range of o·5 to 2·0 per cent (18 to 148/cu. mm.). No age or breed differences were evident and the mean was o·2o per cent (13·3/cu. mm.). "Basket-cells". These were present in 8·6 per cent of animals with a range of 2 to 22j2oo leucocytes. No age or breed differences were evident and the mean was 0·74/200 leucocytes. DISCUSSION
The mean RBC of the I 52 bulls, 7• I 4 million/cu. mm ± I· I 3, was I· I million lower than the figure quoted by Fraser (i 930) for five stall-fed bulls and approximately o·5 million lower than that found by Scarborough (1931). It is 1·2 million higher than the figure for cows quoted by Holman (1955), although this worker has emphasized the danger of such comparisons, because of differences in environment. Greatorex (1957a) observed below-average RBC in cows of the Channel Island breeds and in this study the RBC and the PCV of Guernsey bulls were significantly lower than the figures for Friesians (P < o·o 1). The mean PCV of Friesian bulls for the period three to eight years of age was significantly higher than for the other two periods. A similar though not significant trend was observed with the Hb. Comparable changes have been observed for the PCV and Hb over the lifetime of the human male (Hawkins, Speck & Leonard, 1954). It is of interest that reticulocytes were found in three bulls, one Guernsey and two Ayrshires, and that the RBC counts of these animals were all below the mean for the breed. A few Heinz bodies were observed in a further four bulls (all bled during October) and may possibly have been related to the feeding ofkale (Penny, David & Wright, 1961, 1964). They were all Friesians and their RBC counts were all above the mean for the breed. Although there were no significant trends in the MCV and MCHC, the MCV tended to follow the pattern of the PCV, suggesting the possibility of an increased cell size during the period three to eight years of age. The nine Herefords showed a significantly lower MCV than the other breeds. This was
- BRITISH VETERINARY JOURNAL,
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probably due to a lower PCV, although this could not be proved, owing to a shortage of readings for bulls in the three .to eight-year age group, for which the mean PCV was calculated. The WBC followed the trend described by Holman (I 956) for cows, falling from 9,8oo during the first year of life to 5,970 by three years of age, thereafter remaining reasonably constant. Fraser (I 930) reported a WBC of 6,900 for five stall-fed bulls, which is similar to our figure for bulls of two years and over (6,o8o ± 1,910). Variation in the numbers of lymphocytes was mainly responsible for the changes in the WBC. During the first seven years of life there was an increase in the percentage of neutrophils and a decrease in the percentage of lymphocytes, a reverse of the change reported for the heifer calf in the first year of life (Holman, 1956; Greatorex, 1957h). Analysis of the absolute counts showed that the neutrophil count did not significantly change, but the lymphocyte count decreased more than the percentages alone suggested. The drop in the WBC · over the first year was largely due to a decrease in the number of lymphocytes. In subsequent years the fall in lymphocytes was four times greater than the corresponding rise in neutrophils. The crossover of both the absolute counts and the percentage counts occurred between the fifth and sixth years, and at seven years both the neutrophil and lymphocyte counts became more stable. Moberg (I955) reported a decrease in the numbers ofneutrophils and lymphocytes, and an increase in eosinophils with age in the cow, changes he associated with reproductive phenomena. The number of non-lobulated neutrophils observed was small and is similar to that reported for the cow (Greatorex, I957a; Holman, I955)· The number of basophils was very small and is similar to values reported for the cow (Fraser, 1930; Holman, I 955). The occurrence of so-called "basket-cells" was infrequent and not apparently relate9 to either the breed or the age of the bull. A group of bulls are now being bled at regular intervals during their lifetime in an attempt to demonstrate similar changes in the blood picture of the individual animal. It is hoped thjit these investigations will help to lay down standards which may prove of value in the study of such conditions as the bovine leucosis complex. The results reported here emphasize the advantages, when considering the differential WBC, of dealing in absolute values rather than percentages. ACKNOWLEDGEMENTS
We wish to acknowledge the help received from the staffofHorlicks Farms and Dairies Limited. We are once again deeply indebted to Professor C. S. G. Grunsell for his advice and criticism and we should also like to thank Miss Esme Gray for technical assistance. REFERENCES
FEDERATION OF UNITED KINGDOM MILK MARKETING BoARDS (I963). United Kingdom Dairy Facts and Figures.
HAEMATOLOGICAL VALUES FOR THE BULL
247
FRASER, A. C. ( 1930). Rep. Inst. Path. Uniu. Camb., 1, 114. GREATOREX,]. A. ( 1957a). Br. uet. ]., 113, 29. GREATOREx,J. A. (1957b). Br. uet. ]., 113,469 HAWKINS, W. W., SPECK, E., & LEONARD, V. G. (1954). Blood, 9o 999· HoLMAN, H. H. (1955). Br. uet. ] ., 1:11,440. HoLMAN, H. H. (1956). Br. uet.]., 112,91. McCAY, C. M. (1931 ). ). Dairy Sci., 14> 373· MoBERG, R . (1955) . Quoted from: Schalm, 0. W. (1961). Veterinary Haematology. London: Bailliere, Tindall & Cox. PENNY, R. H. C ., DAVID, J . S. E., & WRIGHT, A. I. (1961) . Vet. Rec., 73• 747· PENNY, R . H. C., DAvm,J. S. E., & WRIGHT, A. I. (1964). Vet. Rec., 76, 1053. PENNY, R. H. C., WRIGHT, A. 1. , & STOKER, J . W. (1964). Br. uet. ]., 120, 286. ScARBOROUGH, R. A. (1931 ). Yale]. Bioi. Med., 4• 69. (Accepted for publication I March, I 966)
122,
239
HAEMATOLOGICAL VALUES FOR THE CLINICALLY NORMAL BULL By R. H. C. PENNY and A. M. ScoFIELD, Department of Veterinary Medicine, University of Bristol,
and H. CEMBROWICZ, Horlicks Farms and Dairies Limited, Ilminster
SUMMARY The blood picture of 152 bulls standing at artificial insemination centres is described. The data obtained were analysed by breed and by age, and significant between-breed and age differences were found . The advantage of using absolute values for the differential white blood cell count is emphasized.
A number of workers have studied individual aspects of the blood picture of the bull (e.g. Fraser, I930; Scarborough, I93I; McCay, I93I), but no detailed study has been made. Holman (I955) has criticized comparisons made between cows and bulls because of differences in their environmental conditions. In I g62 approximately I ,ooo bulls were being kept in insemination centres (Federation of U.K. Milk Marketing Boards, I963). This paper describes the blood picture of such bulls. MATERIALS AND METHODS General All the I 52 clinically normal bulls examined were "standing" at local insemination centres, and blood samples were collected over a two-year period. The jugular vein was used for sampling and the dipotassium salt of Sequestrene (ethylenediaminetetra-acetic acid) was used as an anticoagulant in all cases. All the bleedings were performed in the morning.
Haematological estimations The red cell count (RBC), packed cell volume (PCV), haemoglobin estimation (Hb), reticulocyte count, Heinz body count, total white cell count (WBC) and differential WBC were determined by techniques previously described (Penny, Wright & Stoker, I964; Penny, David & Wright, I964). The mean corpuscular volume (MCV), the mean corpuscular haemoglobin concentration (MCHC) and absolute values for the differential WBC were calculated.
t""
TABLE
II
NORMAL HAEMATOLOG1CAL VALU ES FOR TilE BULL
Breed No . of bulls RBC (106{cu. m:m. ) Hb (g. % ) PCV (%) [I & 2] MCV (cu. J.l) MCHC (% ) (Io 3fcu.
WBC < 2 years
mm.) [2]
> 2 years Dijferential leucocyte count: [3] Neutrophils (%) (1o 3{cu. mm. ) Lymphocytes (%) (1oS{cu. mm.) Monocytes (% ) (per cu. mm. ) Eosinophils (% ) (per cu. mm. )
Friesian
Hereford
Slwrthorn
Charolais
Guernsry
Ayrshire
All breeds
74
9
16
5
28
20
I 52
7"43± I·26 I3"9 ± I·go 43"3 ± 2·58(37) s6·1± 9"24 33"7± 5"02
7"45± I·o6 I3"3± I·s8 38·o(2) 48·6± 6·g3 38·o± 2"34
6·8o± I"04 13"9 ± I·67 42 "2± 5"49(7) 6I ·6± I3·48 32·6± 4·g8
g·Bo ± 3·s6(I I) s ·8s ± 2"45(63 )
g·ss(2)
-
43"2± 8·8g(26) 2•44 ± 1"31 (26) 39"9± 8·53 (26) 2·18± o·g2(26) 4"83± 4"22 311±271 10"4;:!: s·8o(26 ) 590±354 (26)
9"22 ± I•77(7)
-
3"50± 1"94 384 ± 223
-
-
s ·Bg± 1"47{I6) 32"9± 6·66(g) ! •8!± 0"52 (9) so·8 ± 6·25(9) 2·83 ± 0·73(9) 3"13± 3"4 1 342±245 g·78± 2·6o(g) s67±2s8 (g)
Significance
7"51 ± I·25 I3·I± I•53
-
s6·2± I2·8 5 33"3± 6·75
6·62± o·go 12"9± I"93 40"2± 3"79(I2) 58·8± 7"65 33"2± 3·66
7"52 ± I"35{3 ) 4"75(2)
7•8o ± 2"25(6) 5"91± I ·34(22)
-
33"2± 9"24(10) I·8g± 0"97(10) 47"0± 8·41(10) 2"29± o·gg(10 ) 6·o2± 5"53 290±217 13·0 ± 8·76(10) 57I±257 (10)
-
s ·IO ± 5"02 253±225
-
-
6·92± o·92 I3·s± 2"3I 45"I± 5"12(5) 57"4± 7·8s 3I·g± 3"00 7·65 ± 2"I3(5) 6·IS ± 2"3I(IS ) 3I ·6± 10·8(g) 1·8o ± 1·05(9) 55" 1± g·s8 (g) 3"07± 1"25(9) 3"75± 3"26 204±194 8·33± 4"97(9) 492 ± 341 (g)
The values quoted are means and standard deviations. [1] Means quoted for 3 to 8-year age group only. *=P< o·os [2] Figures in brackets denote the number of animals sampled in each group. ** = P < o·oi [3] Means of the differential count for neutrophils, lymphocytes and eosinophils for bulls 8 years and over.
7"I4 ± I"I3 I3"4 ± I·94 42"7± 3·68(63) s6·g± g·68 33"5 ± 5·og 8·68 ± 2"94(27) 6·o8 ± I·gi(I25 ) 37"7 ± 9"14(54) 2·00± o·g6(54) 4s-6 ± 8·64(54) 2•46 ± 1"02(54) 4·o6 ± 4"20 299±250 1o·s± 6·23(54) s66±313 (54)
NS = Not significant.
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II:
BRITISH VETERINARY JOURNAL, 122, 6
Statistical methods The data for Friesian bulls were first selected and divided into the following age groups: under two years, yearly thereafter up to ten years, and animals over ten years of age. The data .were examined graphically and, where trends were suggested, the material was submitted to an analysis of variance (the variances being assumed the same) or, where linear trends seemed likely, by regression analysis. Where age differences were detected the significant means were identified using the standard error of the mean method, and comparisons between breeds were made using the homogeneous ranges of the data which were determined from the graphs, and verified by statistical analysis. Where no age differences occurred, all the data for the other breeds were used in the calculation of means and standard deviations. Between-breed differences were tested by analysis of variance. The null hypothesis was rejected at and below the 5 per cent level of probability (P < o·os). Means and standard deviations are quoted in the text. RESULTS
Red cell count From a graph of the RBC for the 74 Friesians (Table I), a slight increase with age was suspected. However, regression analysis of these data gave a change of o·o82 million/cu. mm./year, which was not significant. Analysis of variance of the data failed to show any significant age differences. Between-breed analysis of the data from all age groups (Table II) showed the RBC of Guernsey bulls to be significantly lower than that of Friesians (P < o·or). There were. no signific~nt differences between the other breeds. Packed cell volume Analysis of the data for PCV presented in Table I revealed significant differences between the age groups (P
Age Group Breed
Friesian Hereford Shorthorn Guernsey Ayrshire
No. of bulls
< 3years
PCV %
No . of bulls
16 . 7
36·7 ± 4'23 34'4± 2·96 35'0 36'3±2"44 36'4± 3'41
37 2 7 12 5
9 7
All breeds 36·1 ± 3·56 63 40 The values quoted are means and standard deviations.
3-8years
No. of bulls
9years +
43'3±2·58 38·o 42 '2±5'49 40'2±3'79 45'1±5' 12
21
39' 7±2 '92
8 7 8
45'7 ± 4'87 38·9 ± 4'76 41'3 ± 4'55
42' 7± 3·68
44
41 '0±4' 79
PCV %
PCV %
HAEMATOLOGICAL VALUES FOR THE BULL
243
three to eight years in both Guernseys (P
Haemoglobin No significant differences between the age groups in Friesians were demonstrated, although the trend followed that of the PCV (Table I). There were no significant differences between breeds (Table II). Reticulocytes and Heinz bodies Reticulocytes were present in three bulls and ranged from o·o2 to o·6I per cent. Heinz bodies were present in four bulls and the range was o·o2 to 0·36 per cent. Mean corpuscular volume No significant differences between the age groups in Friesians were shown, although the trend followed that of the PCV. Herefords had a significantly lower MCV (Table II) than the other breeds (P
BRITISH VETERINARY JOURNAL,
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6
and older (Table II) showed Friesians to have a higher percentage of neutrophils than the other breeds (P < o·os). However, analysis of the absolute values did not show a significant breed difference for this period. qmphocytes. Distribution of the data for Friesians indicated a decrease in the percentage of lymphocytes up to seven years of age, after which the count remained relatively stable (Fig. 1 ). When the absolute count was plotted it
65 - 6,000
u
50
m :;: 0
45
2 0 ~
40
20
<2
2
4
3
5
6
7
8
9
10
>10
Age (years)
Fig.
1.
Changes with age in the lymphocyte and lobulated neutrophil counts of Friesian bulls. = % lobulated neutrophils 0 0 = absolute number of lobulated neutrophils/cu. mm.
e •
e
-
- - -
•
0 - - - - 0
=
% lymphocytes
=
absolute number of lymphocytes/cu. mm.
revealed a more pronounced decrease than the percentages alone suggested. Regression analysis of the percentage oflymphocytes with age gave a coefficient of -4·1 per cent/year ±o·6g, which was highly significant (P < o·or). Regression using the absolute values showed the decrease in lymphocyte numbers with age for this period to be highly significant (b = o·62 x ro 3 fcu. mm.fyear ±o·r2; P
HAEMATOLOGICAL VALUES FOR THE BULL
245
centages or absolute values were detected and there were no breed differences when all the data were used. Eosinophils. Distribution of the data for Friesians indicated that the percentage of eosinophils increased up to seven years of age, after which no regular increase could be seen. Regression analysis of the percentage of eosinophils with age gave a coefficientofo·72 percent/year ±0·38, which was not quite significant at the 5 per cent level. The absolute values did not show a trend wi~h age. There was a significant correlation between the percentages of eosinophils and lymphocytes at all ages (r = 0·54; P < o·oi). In view of this correlation, and the similarity in the shape of graphs of the percentage of eosinophils and neutrophils with age, the breed means were calculated from the bulls of eight years and older. Analysis of these data failed to reveal any significant breed differences in either percentages or absolute values (Table II). Basophils. These were present in 19·7 per cent of animals, with a range of o·5 to 2·0 per cent (18 to 148/cu. mm.). No age or breed differences were evident and the mean was o·2o per cent (13·3/cu. mm.). "Basket-cells". These were present in 8·6 per cent of animals with a range of 2 to 22j2oo leucocytes. No age or breed differences were evident and the mean was 0·74/200 leucocytes. DISCUSSION
The mean RBC of the I 52 bulls, 7• I 4 million/cu. mm ± I· I 3, was I· I million lower than the figure quoted by Fraser (i 930) for five stall-fed bulls and approximately o·5 million lower than that found by Scarborough (1931). It is 1·2 million higher than the figure for cows quoted by Holman (1955), although this worker has emphasized the danger of such comparisons, because of differences in environment. Greatorex (1957a) observed below-average RBC in cows of the Channel Island breeds and in this study the RBC and the PCV of Guernsey bulls were significantly lower than the figures for Friesians (P < o·o 1). The mean PCV of Friesian bulls for the period three to eight years of age was significantly higher than for the other two periods. A similar though not significant trend was observed with the Hb. Comparable changes have been observed for the PCV and Hb over the lifetime of the human male (Hawkins, Speck & Leonard, 1954). It is of interest that reticulocytes were found in three bulls, one Guernsey and two Ayrshires, and that the RBC counts of these animals were all below the mean for the breed. A few Heinz bodies were observed in a further four bulls (all bled during October) and may possibly have been related to the feeding ofkale (Penny, David & Wright, 1961, 1964). They were all Friesians and their RBC counts were all above the mean for the breed. Although there were no significant trends in the MCV and MCHC, the MCV tended to follow the pattern of the PCV, suggesting the possibility of an increased cell size during the period three to eight years of age. The nine Herefords showed a significantly lower MCV than the other breeds. This was
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probably due to a lower PCV, although this could not be proved, owing to a shortage of readings for bulls in the three .to eight-year age group, for which the mean PCV was calculated. The WBC followed the trend described by Holman (I 956) for cows, falling from 9,8oo during the first year of life to 5,970 by three years of age, thereafter remaining reasonably constant. Fraser (I 930) reported a WBC of 6,900 for five stall-fed bulls, which is similar to our figure for bulls of two years and over (6,o8o ± 1,910). Variation in the numbers of lymphocytes was mainly responsible for the changes in the WBC. During the first seven years of life there was an increase in the percentage of neutrophils and a decrease in the percentage of lymphocytes, a reverse of the change reported for the heifer calf in the first year of life (Holman, 1956; Greatorex, 1957h). Analysis of the absolute counts showed that the neutrophil count did not significantly change, but the lymphocyte count decreased more than the percentages alone suggested. The drop in the WBC · over the first year was largely due to a decrease in the number of lymphocytes. In subsequent years the fall in lymphocytes was four times greater than the corresponding rise in neutrophils. The crossover of both the absolute counts and the percentage counts occurred between the fifth and sixth years, and at seven years both the neutrophil and lymphocyte counts became more stable. Moberg (I955) reported a decrease in the numbers ofneutrophils and lymphocytes, and an increase in eosinophils with age in the cow, changes he associated with reproductive phenomena. The number of non-lobulated neutrophils observed was small and is similar to that reported for the cow (Greatorex, I957a; Holman, I955)· The number of basophils was very small and is similar to values reported for the cow (Fraser, 1930; Holman, I 955). The occurrence of so-called "basket-cells" was infrequent and not apparently relate9 to either the breed or the age of the bull. A group of bulls are now being bled at regular intervals during their lifetime in an attempt to demonstrate similar changes in the blood picture of the individual animal. It is hoped thjit these investigations will help to lay down standards which may prove of value in the study of such conditions as the bovine leucosis complex. The results reported here emphasize the advantages, when considering the differential WBC, of dealing in absolute values rather than percentages. ACKNOWLEDGEMENTS
We wish to acknowledge the help received from the staffofHorlicks Farms and Dairies Limited. We are once again deeply indebted to Professor C. S. G. Grunsell for his advice and criticism and we should also like to thank Miss Esme Gray for technical assistance. REFERENCES
FEDERATION OF UNITED KINGDOM MILK MARKETING BoARDS (I963). United Kingdom Dairy Facts and Figures.
HAEMATOLOGICAL VALUES FOR THE BULL
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FRASER, A. C. ( 1930). Rep. Inst. Path. Uniu. Camb., 1, 114. GREATOREX,]. A. ( 1957a). Br. uet. ]., 113, 29. GREATOREx,J. A. (1957b). Br. uet. ]., 113,469 HAWKINS, W. W., SPECK, E., & LEONARD, V. G. (1954). Blood, 9o 999· HoLMAN, H. H. (1955). Br. uet. ] ., 1:11,440. HoLMAN, H. H. (1956). Br. uet.]., 112,91. McCAY, C. M. (1931 ). ). Dairy Sci., 14> 373· MoBERG, R . (1955) . Quoted from: Schalm, 0. W. (1961). Veterinary Haematology. London: Bailliere, Tindall & Cox. PENNY, R. H. C ., DAVID, J . S. E., & WRIGHT, A. I. (1961) . Vet. Rec., 73• 747· PENNY, R . H. C., DAvm,J. S. E., & WRIGHT, A. I. (1964). Vet. Rec., 76, 1053. PENNY, R. H. C., WRIGHT, A. 1. , & STOKER, J . W. (1964). Br. uet. ]., 120, 286. ScARBOROUGH, R. A. (1931 ). Yale]. Bioi. Med., 4• 69. (Accepted for publication I March, I 966)