O. Hanus et al., CALIBRATION AND ACCURACY CONTROL IN DETER MINING SOMATIC-CELL COUNT IN COWS MILK BY MEANS OF THE METHOD FOSSOMATIC, Zivocisna vyroba, 38(10), 1993, pp. 907-926
The presented work deals with the correspondence of determining the so
matic cell count (PSB) in raw and thermally treated milk. Milk samples
(n = 10) have been used with PSB from 112 to 721 thousand/ml, the ari
thmetic average was 329 +/- 212 and the geometric average 274 thousand
/ml. Samples of raw (S) and pasteurized (P) milk were measured non-con
served (N) and conserved by means of K2Cr2O7 (D) and bronopol (BSMT) a
nd by means of devices (Fossomatic 90, Foss Electric, Denmark) with di
fferent levels of discrimination (DL), as well as by means of the dire
ct microscopic method (MM). The question of the principle of calibrati
ng the method F is being discussed in relation to the existence of sou
rces of fluorescence impulses, whether of a parasitic origin (''non-ce
ll'', i.e. chemical, biochemical, resp. microbial origin), or the cell
(somatic) origin.Further the question of potential oscillations of th
e frequency display of parasitic and cell impulses is being discussed
from the point of view of fluorescence peak and under the effect of ce
rtain factors - cow's individuality, mastitis, thermal treatment of mi
lk (Fig. 1 and 6). At all DL levels used, there are - with exceptions
- significant differences (P < 0.05) between the samples S and P. The
samples P show always higher values: with increasing DL the registered
PSB decreased markedly and significantly in samples S and non-signifi
cantly in samples P; PSB of samples P decreased significantly with gro
wing DL with subthreshold values of the device F used which applies ge
nerally for differently preserved samples (Tab. I and III). It follows
from the results that thermal denaturing effects during pasteurizatio
n increase the colouring ability of cell nuclei and displace the distr
ibution of cell impulses, probably increase the frequency and change a
lso the distribution of parasitic impulses (Fig. 2 and 6). Differences
between the samples D and N and BSMT and N within the samples S were
greater and significant in some cases and they were small and predomin
antly non-significant between BSMT and D within S, as well as with all
preservation methods within the samples P (Tab. II and IV). As expect
ed, the differences in the direct microscopical method between the var
iants S and P was slight(P > 0.05, Tab. V). In case an optimal thresho
ld according to MM and the curve of threshold S (Fig. 2, D, I) = 0.98
was determined for the results mentioned, a distinct intercept change
applies for the equation P (Tab. VI, Fig. 3). In opposite, if the thre
shold has been defined according to the curve P = 3,90, a distinct cha
nge of slope applies for the equation S (Tab. VI, Fig. 4). That is why
the average values of PSB divert distinctly and significantly (P < 0.
01 and P < 0.001) from MM (Tab. VI) in both cases. A good closeness of
the relationship of determining PSB between MM and F with different D
L has been assessed (Tab. VI, r = P < 0.001). A potential adjustment o
f DL according to samples P during routine measurement of samples S is
, therefore, not appropriate. Fig. 6 shows an attempt to describe chan
ges in the distribution of impulses due to pasteurization. As correct
can be considered only a delimination, resp. a potential adjustment of
DL according to the re suits of MM in samples measured in a routine w
ay, i.e. with a similar distribution of the size of fluorescence impul
ses. For the control of calibration stability in time (without the aim
of adjusting DL), also repeatability of measurement in material with
changed distribution of impulses (thermally treated milk) can be used.
Lintner et al. (1984) and Szijarto, Barnum (1984) used pasteurized mi
lk just only for the control of calibration stability in time and not
for a