O. Hanus et al., RELATIONSHIP BETWEEN THE FERMENTATION OF BULK MILK SAMPLE, ITS COMPOSITION AND CONTENTS OF SOME METABOLITES, Zivocisna vyroba, 38(7), 1993, pp. 635-644
The fermentation is a significant technological property of milk and i
ts determination enables to evaluate the suitability of the raw materi
al for the production of fermented milk products. The relationship bet
ween the composition of a bulk milk sample and the fermentation was ob
served after excluding samples with a positive evidence of the presenc
e of inhibitory substances, especially of an antibiotic character, by
means of a microbiologic method (Bac. stearothermophilus, the IN-test)
. The number of samples according to individual parameters observed wa
s 124, 358 and 535 (Tab. I). The following parameters have been observ
ed: milk fermentation (the yoghourt-test - JT) after milk pasteurizati
on; the content of fat (T), proteins (B), lactose (L), non-fat solid (
TPS), dry matter (S), urea (M), acetone (A), and nitrates (D); titrabl
e acidity (SH) and actual acidity (pH); somatic cell count (PSB); cond
uctivity (gamma). Tab. I summarizes basic values and the variability o
f parameters observed. The greatest variability was noted with paramet
ers having a close relationship to the health and metabolic state of t
he organism of milk cows: D, A, PSB, gamma, M, and JT. The lowest vari
ability was found with TPS. Results of the correlation analysis are be
ing summarized in Tab. II. Milk fermentation was in a significant rela
tionship with decreased dependence on pH (r = -0.42, P < 0.0 1), PSB (
r = -0,23, P < 0.01), M (r = -0.23, P < 0.01), A (r = -0.21, P < 0.05)
and further on SH, B, L, and TPS. The negative relationship to PSB me
ntioned in literature as well documents a frequent occurrence of techn
ological difficulties with processing of milk from cows with a deterio
rated udder health state. Probably for the first time a negative relat
ionship between JT and A was noted. With regard to the positive relati
onship of fermentation to B and negative relationship to M and A, JT w
ill be in a narrower negative dependence on the deficiency of energy i
n the nutrition of cows, with decreasing content of milk proteins and
increasing content of undesirable metabolites M and A. This also indic
ates the method of evaluation used in Tab. III. JT values were divided
into classes (I to 9) according to the content of B and M in milk wit
h a premise of supply of feed nutrients in the feed ration. Significan
t differences of the classes 2 and 7 compared with 1 (a balanced suppl
y of energy and nitrogen substances in the nutrition with regard to ac
tual milk yield is being presupposed) and the total trend of results i
ndicate a decrease in JT values with a presupposed energy deficiency i
n the nutrition. The relationship between JT and nitrate content was n
on-significant (P > 0.05). The following correlation relationships (Ta
b. II) are interesting as well: B x A (r = -0.22; P < 0.01), PSB x L (
r = -0.39; P < 0.01), SH x PSB (r = -0.25; P < 0.01), SH x A (r = -0.
17; P < 0.01) and the relationship of gamma to T, L, TPS and SH. The r
elationship between L and M (r = -0.51; P < 0.01), when confirmed by a
further research, could be used for a routine evaluation of the udder
health state and supply of feed nutrients in cows according to the va
lues of PSB and L or, as the case may be, for a specification of concl
usions according to the values of PSB, B, M, and L in individual cows.
It is generally known (H a n u s et al., 1992a, b) that the closeness
of dependence between PSB and L decreases with an ameliorating udder
health state. A confirmation of the hypothesis that, in opposite, the
closeness of relationship between L and M increases with the ameliorat
ing udder health state would mean an increased probability of the stat
ement that - with a lower PSB (< 300 thous./ml) - the markedly decreas
ed lactose content indicates a deficiency of energy in the feed ration
(which could routinely be used in breeding). The results obtained giv
e no answer to the question whether a deteriorated fermentation which
accompanies increased levels of some undesirable metabolites could be
the consequence of the effect of these very metabolites alone.