Variation in blood leucocytes, somatic cell count,

yield and composition of milk of crossbred goats

Mainak Das, Mahendra Singh*

Dairy Cattle Physiology Division, National Dairy Research Institute, Karnal 132001, Haryana, India

Accepted 12 June 1999

Abstract

Ten multiparous crossbred goats, ®ve each of alpine � beetal (AB) and saanen � beetal (SB) were selected from the

National Dairy Research Institute goat herd immediately after parturition. These were managed as per the practices followed

in the institute's goatherd. Blood and milk samples were collected at biweekly intervals from day 14 post-kidding for 22 weeks

(154 days). Somatic cell count, electrical conductivity, fat, protein and lactose contents of milk were determined using

standard methods. In the blood samples total leucocytes and differential leucocytes were also determined. Somatic cell counts

were high immediately after parturition on day 14 of lactation and declined gradually with advanced lactation. There were

individual variations (P < 0.01) in somatic cell counts between different lactation periods. Somatic cell count of milk was

negatively correlated with neutrophils only (P < 0.05) and was neither correlated with milk yield, or with fat, protein, lactose

content of milk. Electrical conductivity of milk was low up to four weeks of lactation and thereafter increased as the lactation

advanced. Lactose content of milk declined gradually with the advancement of lactation. Fat content of milk was stable up to

the eighth week and thereafter increased with advancement of lactation while the protein content of milk did not change

signi®cantly during lactation. # 2000 Elsevier Science B.V. All rights reserved.

Keywords: Somatic cell counts; Blood cells; Electrical conductivity; Milk composition; Crossbred goats; Lactation

1. Introduction

The somatic cells that are sloughed off during the

normal course of milking have been characterized as

an index of udder in¯ammation like mastitis and for

the assessment of suitability of milk for marketing and

for manufacturing purpose (Smith and Roquinsky,

1977). The normal secretion in goats consists of

cytoplasmic particles, which break off and are shed

with the milk. Stage of lactation and season also affect

secretion of somatic cell counts in the milk (Dulin

et al., 1983; Lee et al., 1994; Wilson et al., 1995).

Information on the pattern of change of somatic cell

counts during entire lactation and also season in

crossbred goats under tropical condition is not avail-

able. The present study was therefore undertaken to

determine the levels of somatic cells in milk during

different stages of lactation and possible relations, if

any, with haematological parameters viz., total leuco-

cytes, lymphocyte, monocyte, neutrophil, eosinophil,

basophil and the yield and composition of milk.

Small Ruminant Research 35 (2000) 169±174

* Corresponding author. Fax: �91-0184-250042.

E-mail address: ndri@x400.nicwg.nic.in (M. Singh).

0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.

PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 0 8 8 - 7

2. Materials and methods

2.1. Experimental

Ten healthy crossbred goats, ®ve alpine � beetal

(AB) and ®ve saanen � beetal (SB) were selected

from the Institute's goatherd immediately after par-

turition. The experiment was started during the month

of November, 1996 and continued up to April, 1997

for a period of 22 weeks. All experimental goats were

in their second or third lactation. For the entire experi-

mental period goats were kept in a loose housing

system with brick ¯ooring. They received ad lib green

fodder, which consisted of berseem (Trifolium alex-

andrinum) and mustard (Brassica campestris). The

concentrate mixture having 70% total digestible nutri-

ents and 20% crude protein was fed based on milk

production (400 g per kg milk) at the time of milking.

The water was offered ad libitum to all the goats.

2.2. Blood and milk samples

The goats were hand-milked at 5:00 and 17:00

hours daily and the milk yields were recorded. Well

mixed milk samples were collected during morning

milking at biweekly intervals for 154 days. Aliquots of

milk samples from each goat in proportion to their

milk yields were taken and used for analysis of milk

constituents. Jugular blood samples were collected in

heparinized vacutainer tubes at 05:00 hours before the

start of milking. The maximum and minimum ambient

temperatures, relative humidity and vapor pressure

were also recorded during the period of study.

2.3. Statistical analysis

Statistical analysis of data was carried out using

two-way analysis of variance (ANOVA) as described

by Snedecor and Cochran (1980). Mean and standard

error of the different parameters and the correlations

among the parameters were calculated for each

biweekly period.

2.4. Analytical methods

In the fresh milk sample from each goat, milk fat

was determined by Gerber's method (ISI, 1958). The

lactose content of milk was estimated by picric acid

method (Perry and Doon, 1950) and the protein by

formaldehyde titration method (Singhal and Raj,

1989). Electrical conductivity (EC) of fresh milk

was measured using digital conductivity meter (cen-

tury make cc 601) standardized with goat milk.

Somatic cell counts (SCC) in fresh milk were counted

by the method of IDF (1984). l0 ml smear of milk was

made in an area of 20 � 5 mm on a glass slide and the

somatic cells were stained using methylene blue dye.

The somatic cells were counted in 50 ®elds and were

multiplied by the microscopic factor. In fresh blood

samples, total leucocyte count (TLC) and differential

leucocyte counts (DLC) namely, lymphocyte, mono-

cyte, neutrophil, eosinophil and basophil cells were

determined by the method of Jain (1986).

3. Results

Mean somatic cell counts, yield and composition of

milk and electrical conductivity for different experi-

mental periods has been shown in Table 1. The

average maximum and minimum ambient tempera-

tures varied from 16.738C to 29.378C and 4.468C to

15.358C during the experimental period. The average

values of THI (temperature humidity index) during

morning and evening were 49.35±76.67 and 48.95±

78.00, respectively. Mean SCC was higher during the

®rst biweekly period of lactation and declined steadily

with advanced lactation, but in individual goats con-

siderable variation (8.09±44.10 � 105 cells/ml) in

SCC existed. Goat AB-138 had very high SCC in

comparison to other goats from the beginning to the

end of the experiment. The goat when tested for

mastitis using California mastitis test was found to

have normal milk. On the other hand in another goat

SB-536, SCC was very low and varied between 5.50

and 8.09 � 105 cells/ml during lactation which indi-

cated that SCC varied between the animals. The

variations in SCC between the goats and between

different experimental periods were highly signi®cant

(P < 0.01). Further, the variation in SCC between the

two breeds of goats was also signi®cant (P < 0.05).

The SCC changes were almost stabilized from the

sixth biweekly period to the end of lactation. Cyto-

plasmic particles were more in early lactation as

compared to mid-lactation (data not presented). Elec-

trical conductivity of milk was low during ®rst two

170 M. Das, M. Singh / Small Ruminant Research 35 (2000) 169±174

Table 1

Mean � standard error values of somatic cell counts, yield, percentage of fat, protein and lactose and electrical conductivity

Parameters Experimental period (biweekly)

1 2 3 4 5 6 7 8 9 10 11

Somatic cell count

(�105 cells/ml)

15.18 � 3.11 12.31 � 1.70 10.48 � 0.92 9.50 � 0.89 9.40 � 0.75 9.00 � 0.77 8.92 � 0.72 9.11 � 0.64 9.51 � 0.70 8.75 � 0.54 8.04 � 0.49

Milk yield (kg) 1.08 � 0.20 1.61 � 0.16 1.83 � 0.14 1.80 � 0.10 1.56 � 0.08 1.31 � 0.09 1.27 � 0.10 1.17 � 0.09 1.20 � 0.11 1.05 � 0.09 0.97 � 0.06

Fat (%) 3.48 � 0.06 3.58 � 0.07 3.43 � 0.09 3.46 � 0.08 3.61 � 0.06 3.58 � 0.05 3.71 � 0.04 3.84 � 0.06 3.96 � 0.05 4.27 � 0.05 4.32 � 0.05

Protein (%) 2.64 � 0.06 2.68 � 0.06 2.71 � 0.04 2.82 � 0.06 2.77 � 0.05 2.75 � 0.05 2.73 � 0.03 2.79 � 0.04 2.74 � 0.08 2.74 � 0.09 2.68 � 0.09

Lactose (%) 5.00 � 0.14 5.02 � 0.19 4.89 � 0.15 4.72 � 0.18 4.63 � 0.16 4.48 � 0.17 4.41 � 0.18 4.43 � 0.17 4.35 � 0.17 4.33 � 0.16 4.22 � 0.16

Electrical conductivity

(mhos)

2.10 � 0.03 2.01 � 0.01 2.15 � 0.04 2.36 � 0.05 2.48 � 0.06 2.86 � 0.05 3.13 � 0.06 3.72 � 0.11 4.10 � 0.13 3.69 � 0.08 3.53 � 0.06

Table 2

Mean � standard error value of hematological parameters for the experimental period

Parameters Experimental period (biweekly)

1 2 3 4 5 6 7 8 9 10 11

Total leucocyte

count (�103 cells/ml)14.71 � 0.59 14.95 � 0.60 14.55 � 0.58 14.29 � 0.57 14.04 � 0.55 13.98 � 0.59 14.13 � 0.57 14.38 � 0.55 14.63 � 0.61 13.80 � 0.56 13.51 � 0.63

Lymphocyte (%) 55.50 � 0.79 55.80 � 0.98 57.40 � 0.98 59.00 � 1.09 60.30 � 1.01 61.40 � 1.13 61.20 � 1.41 60.80 � 1.12 60.50 � 0.85 59.30 � 1.08 58.60 � 1.09

Monocyte (%) 5.30 � 0.43 4.80 � 0.54 3.10 � 0.54 0.90 � 0.48 0.10 � 0.09 0.10 � 0.09 0.30 � 0.20 1.60 � 0.53 1.20 � 0.56 1.80 � 0.64 2.50 � 0.53

Neutrophil (%) 33.60 � 0.65 34.40 � 0.01 35.40 � 0.75 37.10 � 0.71 37.80 � 1.15 37.80 � 1.14 37.60 � 1.62 36.50 � 1.54 36.60 � 1.31 37.20 � 1.42 35.90 � 1.40

Eosinophil (%) 4.80 � 0.46 4.10 � 0.79 3.10 � 0.87 2.30 � 1.00 1.80 � 0.64 0.70 � 0.28 0.70 � 0.25 0.80 � 0.28 1.20 � 0.42 1.10 � 0.39 1.70 � 0.32

Basophil (%) 0.80 � 0.19 0.90 � 0.26 0.80 � 0.31 0.70 � 0.45 ± ± 0.20 � 0.13 0.40 � 0.15 0.50 � 0.21 0.50 � 0.16 1.30 � 0.40

Table 3

Summary of ANOVA of complete data on SCC, milk yield and composition, EC and the hematological parameters

Source of variation d.f Mean sum of square

SCC Milk yield Fat Protein Lactose EC TLC Lymphocyte Monocyte Neutrophil Eosinophil Basophil

Between animals 4 12454b 0.315 0.281b 0.163b 1.31b 0.090 1940.8a 49.99b 10.42b 15.26 5.33a 1.468

Between groups 1 7767a 0.511 0.131a 1.035b 0.111 0.029 126.6 102.15b 18.41b 856.81b 191.14 0.582

Between

experimental period

10 4186b 0.917b 0.981b 0.286 0.790b 5.657b 249.2 43.00b 32.34b 19.61b 19.94b 1.485a

Error 94 1227 0.142 0.313 0.286 0.267 0.055 314.8 9.90 1.87 6.29 1.63 0.657

aP < 0.05.bP < 0.01.

M.

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169±174

171

periods and increased thereafter till the ninth experi-

mental period of lactation (P < 0.01). The signi®cant

changes in EC (P < 0.01) during different periods of

experiment with no changes in EC of two breeds of

goats and between the goats indicated that EC of milk

changes with stages of lactation. Percentage of fat,

protein and lactose of milk varied (P < 0.01) between

the animals. The percentage of fat and lactose also

varied signi®cantly during different stages of lactation

(P < 0.01) but the protein content did not vary during

different periods of lactation. Somatic cell counts were

not correlated with any of the parameters viz., milk

yield, fat, protein, lactose and electrical conductivity

of milk. EC of milk was positively correlated with fat

content of milk (P < 0.01) and negatively with lactose

and milk yield. Fat content of milk was negatively

correlated with lactose (P < 0.01) and milk yield

(P < 0.05).

3.1. Hematology of the goats during lactation

The mean values of hematological parameters and

the summary of ANOVA of all parameters (Tables 2

and 3) showed that mean TLC was 14.95 � 103 cells/

ml during second period of lactation and declined

gradually to low values of 13.98 � 103 cells/ml in the

sixth period of lactation and thereafter ¯uctuated. The

changes in TLC during different experimental periods

in both breeds of goat were not signi®cant. Blood

lymphocytes also exhibited an increase in cell number

upto the 12th lactation and thereafter ¯uctuated being

50±70% in both the AB and SB breed. Due to greater

variability (P < 0.01) in lymphocytes of the two

breeds, the changes in blood lymphocytes between

different lactation periods and between the animals

were signi®cant (P < 0.01). The monocyte numbers

varied between 4 and 9% with mean values of 5.30%

during the ®rst two biweekly periods of lactation and

thereafter declined. During the ®fth and sixth periods

of lactation the monocyte counts were minimal and in

some of the goats was absent beginning fourth period

of experiment. Due to greater individual variation, the

changes in monocytes between the goats and between

different periods of lactation were signi®cant (P <

0.01). Further, breed difference in monocyte counts

was also signi®cant (P < 0.01). Average values of

blood neutrophils were low during the ®rst period,

increased gradually up to the seventh period and

thereafter remained ¯uctuating. On percent basis dur-

ing entire lactation of 154 days neutrophils were 30±

47%. The changes in neutrophil cell numbers between

animals were not signi®cant while differences in

experimental periods were signi®cant (P < 0.01).

The changes in neutrophil percent of the two breeds

of goats were also signi®cant (P < 0.01). Blood eosi-

nophils were high during the ®rst period and declined

as lactation advanced up to the sixth period of lacta-

tion. The pattern of change in eosinophil was similar

to the changes observed for blood monocytes. In some

of the goats, the eosinophils were almost absent in the

blood from the fourth period of lactation and there-

after, while in the remaining goats, their number

varied between 1% and 8% only. The variation in

eosinophils between the goats and during different

fortnights of lactation were highly signi®cant

(P < 0.01). However, both breeds of goats did not

exhibit signi®cant changes in eosinophil counts during

different lactation periods. Blood basophil cells did

not exhibit a distinct change during entire lactation.

The basophil were absent in blood of AB cross from

the ®fth period of lactation while in SB crosses, the

cells were absent from third to seventh period of

lactation. Since there was no distinct pattern of change

in basophils in different goats, the changes in the

basophil cells between animals and between breeds

were not signi®cant. However, variations in basophil

cells were signi®cant (P < 0.05) between lactation

periods.

4. Discussion

In the present study the SCC in different goats were

highly variable during different periods of lactation.

The high SCC in goat AB-138 was probably due to

inherent characteristics, as the goat udder remained

healthy throughout the period of study. The SCC

values observed in this study were similar to earlier

reports in goat (Park, 1991; Haenlein, 1987; Randy et

al., 1991; Hahn, 1992). The SCC are in¯uenced by

season, stage of lactation and productive stage of the

goats (Dulin et al., 1983; Randy et al., 1991; Wilson et

al., 1995; Muggli, 1995). Kasireddy (1983) reported

that SCC increase during second half of lactation and

were inversely related to milk yield. Hinckley (1984)

reported high SCC and high amounts of cytoplasmic

172 M. Das, M. Singh / Small Ruminant Research 35 (2000) 169±174

particles in goat milk as observed in this study. Fat and

protein percents were signi®cantly correlated with

SCC in goat milk representative samples (Park and

Humphrey, 1986) but such correlations were not found

in the present study. Further, the kidding of goats

occurred in the month of November and lactation

continued up to April, but the effect of temperature

on SCC and other parameters studied was not clearly

discernible in this study. The trend in SCC during

different periods of lactation indicated that SCC

remains high during early lactation and with establish-

ment of lactation the SCC gets stabilized to basal

levels. The change in EC during lactation period was

in¯uenced by change in milk yield during lactation but

there was no correlation between SCC and EC of milk

as reported earlier by Park (1991). However, Lee et al.

(1994) reported a close relationship between SCC and

proportions of raw goat milk from individual goats

sampled once in a month. SCC from individual goat

milk was higher than those in goat bulk milk. EC of

milk depends on the concentration of cations and

anions in milk. Since sodium and chloride content

of milk increase during late lactation, the EC of milk

also increases with stage of lactation. The decline in

total leucocyte counts, basophils, eosinophils and

monocytes up to ®fth period of lactation indicated

their migration from blood into milk for more ef®cient

phagocytosis and mammary gland defense against

pathogens (Paape et al., 1992). Hinckley and Williams

(1981) reported poor correlation between SCC and the

leucocyte count. The role of neutrophils in lactation is

not clear but the increase in neutrophils may probably

be due to the increase in milk yield during early

lactation and thus contribute to high SCC in milk

(Drake et al., 1992). Since lymphocytes are of differ-

ent types, their role in lactation can only be predicted

when different types of lymphocytes are determined.

El-Nouty et al. (1984) reported that during mid-

lactation lymphocyte numbers increase while remain-

ing types of leucocyte decrease as observed in this

study also. The individual variations in cell numbers

and the absence of monocytes, basophils and eosino-

phils in the blood during certain periods of lactation

indicated that these cells probably do not have any

signi®cance with stage of lactation and the SCC of

milk, and therefore, it is very dif®cult to establish

reference values of these cells in goats (Masoni, 1985).

The decline in lactose percent concomitant to decrease

in milk yield and increase in fat content with advance-

ment of lactation was also reported earlier in goat

(Mukherjee et al., 1985; Zyugoyiannis and Katsaou-

nis, 1986; Kalla and Prakash, 1990; Simos et al.,

1991). However, Singh (1996) reported variation in

the fat, protein and lactose content of milk and

there was no effect of stage of lactation. From the

study it was concluded that SCC of milk in goats were

high during early lactation and decreased subse-

quently as the lactation advanced. Total leucocyte

count in blood also decreases as the lactation pro-

gresses and remains ¯uctuated during late lactation.

Lymphocytes and neutrophils were low during early

lactation and with establishment of lactation stabilize

to normal levels. Protein content of milk did not vary

during different periods of lactation. However, lactose

decrease and fat percent increase with advancement

of lactation.

Acknowledgements

The authors are thankful to the Director, National

Dairy Research Institute, Karnal for providing the

necessary research facilities to conduct the study.

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