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Milkofix (M), a health friendly preservative substance, to be used for milk sample preservation (Trzický, 1990), was compared with other preservatives. Untreated milk samples (N) were tested against samples treated with sodium azide (A; 0.0085 g NaN3 and 0.0630 g NaCl), bronopol (B; 0.0100 g bronopol and 0.090 g NaCl), potassium dichromate (C; 0.0330 g K2Cr2O7 and 0.0670 g KCl) and Milkofix (M; 0.1250 g). The doses of the preservatives A, B, C and M are per 25 ml milk. The somatic cell counts (SB) were determined on a FOSSOMATIC 90 apparatus (FOSS ELECTRIC, DENMARK). In the treated milk samples taken from individual cows the values of SB counts were significantly higher than in N samples if determined within eight hours after sampling (Tab. I): in A higher by 18.6%, B by 26.3%, C by 26.4% and M by 24.3% (P less than 0.05). The significantly higher values of SB counts were recorded in bulk milk samples treated with preservatives in comparison with N samples immediately after sampling: in A by 6.0%, in B, C and M by 12.9% (P less than 0.01; Tab. II). After one-day storage of N samples at a temperature of 4 degrees C these differences are insignificant (P greater than 0.05), thus the results of N, A, B, C and M samples obtained after one-day storage at 4 degrees C can be taken as actual and mutually comparable.(ABSTRACT TRUNCATED AT 250 WORDS)

The relation between the prevalence of contagious mastitis with the finding of Streptococcus agalactiae and Staphylococcus aureus and the number of somatic cells in the tank samples of milk was studied on the basis of a clinical and bacteriological examination of 11 129 daily cows on four large farms, with a capacity of 600 to 1240 animals. A statistically significant correlation was demonstrated between the analyzed characteristics (r = 0.621). The relation was demonstrated at a prevalence up to 25.3%. The number of somatic cells provides a marked indication of prevalence only from 10%. We failed to demonstrate a statistically significant correlation between the prevalence of mastitis with a cultivation finding of Staphylococcus aureus and the number of somatic cells in tank samples of milk (r = 0.054). The results suggest that on large farms it will not be possible to use only the number of somatic cells in tank milk samples as a signal of diagnostic improvement and preventive mastitis-control measures, since a 10% prevalence of these diseases usually excludes the possibility of herd sanitation.

A positive correlation of the milk specific conductance (MSC) to the number of cells (r = 0.65) and to the content of chloride ions (r = 0.93) was found on the basis of an examination of 196 udder-quarter milk samples. As indicated by the closeness of the relationship to the number of cells, MSC measurement at a determination level of 41.8% has similar diagnostic effectiveness as the determination of the content of chloride ions (determination level 43.5%) and lactose content (determination level 42.8%), and much higher diagnostic effectiveness than the determination of titration acidity (determination level 23.4%). As indicated by the closeness of the relationship to the content of chloride ions, MSC measurement at a determination level of 86.7% has higher diagnostic effectiveness than the determination of lactose content (determination level 73.9%) and titration acidity (determination level 54.6%). In both comparisons, the highest diagnostic effectiveness was found in assessing the chlorine-sugar number (determination levels of 49.8% and 94.0%). The MSC value, corresponding to the cellulization of 500 . 10(3) cells per ml of milk, was determined from regression: 0.523 S . m-1. The diagnostic congruence of MSC with the number of cells in milk was 81.25%, and with the findings of mastitis test-NK only 54.0%. The variability of the measurements of MSC renders it impossible to use this measurement to indirect multi-step screening of milk cellulization. It is only realistic to distinguish two classes of the measured MSC values: negative and positive.

In two cow-houses (fifty cows in each), 5851 udder-quarter samples were subjected to cytological examination (by the Coulter Counter electronic computer) and to bacteriological examination during a ten-month period; the cytological examination was also performed with 141 can milk samples. The mixed samples in which the number of cellular elements does not exceed the level of 500 thousand ml-1 do not indicate reliably whether the milk comes from healthy udder quarters or contains an admixture of secretion from the diseased quarters. A value of above 500 thousand cellular elements per ml in mixed samples only suggests that the milk probably contains more secretion from infected udder quarters. The number of cells in the mixed samples does not constitute a basis for the conclusion concerning the number of quarters with impaired secretion which contributed to the sample, because the number of cells in the mixed samples depends also on the degree of disease in the respective quarters. An amount up to 500 thousand cellular elements per ml in the mixed sample provides practically no useful and usable information on milk quality. If the number of cellular elements per ml is higher than 500 thousand, this information is only suitable for revealing the stables with a high occurrence of mastitis--it is just a signal, not a parameter of such a situation. It is from this aspect that all results should be evaluated at those places where only mixed samples can be examined.

A field trial was performed in two half-sib first-calver groups of the Bohemiam Spotted breed. Each group included thirteen animals, studied for the effect of milking without additional hand stripping on the health condition of the mammary gland for a period of one lactation. The indices of an udder health condition were not affected at an appreciable level of statistical significance (the clinical and bacteriological picture, the positivity of the Mastitis test - NK, the content of milk cellular elements, milk chloride ion content, lactose content, and the value of the chlorine-sugar number. The unstripped udder halves showed a slight increase of the irritation index (by 0.1), milk cellular element content (by 33 000 per per 1 ml), chloride ion content (by 0.81 mmol 1+-1), and chlorine-sugar number (by 0.03). However, the mentioned increase did not exceed the limits of the physiological ranges of the parameters under study - hence it cannot be treated as a sign of udder alteration due to milking without additional hand stripping.

The number of somatic cells and the isolation of the causative agents of mastitis in quarter, composite, bucket, and bulk tank samples of cow's milk was determined four times during a six-month period. The number of somatic cells in milk samples indicated a degree of mastitis infection and was influenced neither by the year season nor by the length of lactation. At a repeated examination of 28 dairy cows an increased number of somatic cells in milk was found once in 68 udder quarters and with three successive samplings only in 21 quarters. The etiological agents of mastitis were detected once in 31 quarters and three times in succession only in five quarters. The number of cows positive by the number of cells in quarter samples of milk increased from 52.9-58.8% at a single examination to as much as 100% at four examinations. The etiological agents of mastitis were isolated in a single examination in 17.6% of cows and at four examinations in 58.8% of cows. The composite and bucket samples of milk containing 200 to 300 thousand cells per ml are recommended to be considered as mastitis-positive: in 68 to 78% they came from cows having more than 500 thousand cells per ml at least in one quarter sample. The number of cells in a bulk sample was in correlation with the percentage of cows having a positive NK-test (similar to CMT) and positive isolation of S. agalactiae from quarter milk samples.(ABSTRACT TRUNCATED AT 250 WORDS)

The somatic cells of cow's milk were separated by filtering through nitrocellulose membrane filters (Synpor), pore size 2 to 5 micron. An indole reagent was added to the membrane filters with trapped cells, the mixture was warmed in boiling water bath for 20 min., then cooled, centrifuged (3500 X g, 15 min.), and optical density was measured at 490 nm. The relation 8 micrograms = 1 million cells was used for the conversion of DNA content in sample to the counts of cells. The average variation coefficient of the determination was 4.7% and the coefficient of correlation between the indole DNA filter method and direct microscopy on membrane filters was r = 0.997. Using the indole DNA filter method, the counts of somatic cells can be estimated from milk samples kept frozen or from filters with retained cells kept at 4 degrees C, or (for a short time--3 days) at 25 degrees C. The estimation is not distorted when the milk samples are stabilized with K2Cr2O7 or a mixture of K2Cr2O7 and HgCl2, if they are kept at 4 degrees C for eight days.

The authors evaluated the method of the determination of the electric conductivity of purchased milk for the estimation of the hygienic aspects of milk quality and for mass diagnosis of the inflammatory diseases of dairy cow mammary glands. The variability coefficient of duplicates varied from 1.37 to 3.09%. The study of the dependence of milk conductivity measurement on milk temperature revealed a statistically highly significant positive correlation between the values of these two factors. In the temperature range from 30 degrees C to 35 degrees C the coefficients of correlation ranged from 0.951 to 0.996. Furthermore, interference caused by milk acidity was examined during a five-day incubation of samples at 25 degrees C. A statistically significant difference was observed from the third hour of incubation (P less than 0.05) and a statistically highly significant difference from the fourth hour of incubation (P less than 0.01). The evaluation of the diagnostic value of the method of the measurement of electric conductivity in purchased milk revealed a positive correlation to the content of chloride ions (r = 0.69) and to the number of the cellular elements of milk (r = 0.33).

Six joint trials were conducted in six diagnostic laboratories equipped with the Coulter Counter Model D electronic computers. The congruence and repeatability of the determination of somatic cell counts in milk were determined in these trials. The results were confronted with similar trials performed in the Netherlands. The average differences in the results of determinations performed in the different laboratories exhibited a tendency of improvement as the joint tests proceeded, so that a satisfactory congruence of the results in all laboratories was obtained in the last trial. The standard deviation of the average difference and the average difference between parallel samples were characterized by high variedness . As found, the calibration of the computers by the plateau-and-trough method is not satisfactory and should be replaced by the calibration method of half the number and by the setting of an equal threshold size of the counted cells. The repeatability of determination will have to be improved by controlling rationing devices for milk dilution and by controlling the standard volumes counted by the apparatuses.

The rapid reaction of the diphenylamine agent with DNA was used for the determination of the counts of somatic cells in cow's milk, using the DNA filter method. The method is based on the filtration of a warmed (65-70 degrees C) mixture of milk with Triton X-100 through the Synpor nitrocellulose membrane filter, pore size 2 to 5 microns, and subsequent DNA determination of the collected somatic cells by the colour reaction of diphenylamine. A 2ml quantity of distilled water and 4 ml of diphenylamine reagent were added to the membrane filters with somatic cells. The mixture is warmed in water bath at 90 to 100 degrees C for 20 min., then it is cooled, centrifuged (3500 X g, 15 min.), and the optical density is measured at 595 nm. The relation 8 micrograms = 1 million cells was used for the conversion of DNA content to the counts of cells. The average variation coefficient of the determination was 5.9% and the coefficient of correlation between the diphenylamine DNA filter method and the direct microscopy of the somatic cells on membrane filters was r = 0.997. Using the diphenylamine DNA filter method, the counts of somatic cells can also be determined from milk samples stored in frozen condition or from the filters with collected cells kept at the temperature of 4 degrees C (10 days) or 25 degrees C (3 days). Milk stabilized with formaldehyde can also be used for the determination if stored at 4 degrees C.