الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
A total of 518 individual quarter milk samples collected from 130 apparently healthy cows examined bacteriologically as well as by screening tests , for detection of subclinical mastitis.
The incidence percentage of subclinical
mastitis among lactating cows was 53.84%, all were due to specific mastitogenic organisms.
The most prevalent causative organisms in
positive samples was Staph. aureus; E . coli, Stah.
epidermidis and Str. uberis in adescending manner ragned between 27.95% (45), 25.47%(41); 18.01% (29) and 11.18% (18), while proteus vulgaris, Str. agalactiae; klebsillae pneumonae and pseudomonas aeruginosa could be isolated from 5.59%; 4.97%, 3.73% and 3.1% respectively.
The rate of who udder infection was compa-ratively low, while the rate of hind’ quarters infection among mastitic cases was comparativelly
high.
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Correlation between screening tests and bacteriological examination revealed variable diff-erences in agreement percentages.
The chloride test revealed a dependability of
75.78% in mastitic milk samples, whereas both
false positive (24.13%) and false negative (5.98%)
results were comparatively high. Therefore , chlo-
rine test cannot be considered as a decisive test for diagnosing subclinical mastitis.
Catalase test showed the highest percent of
accuracy (92.66%). As compared with the bacteriolo-gical findings , all examined milk samples which produce 2.0 ml gas or more proved to be mastitic (100% agreement). In consequent of the highest Percent of false negative results, the apparently
normal milk continue as a problem in animal health, beside its public health hazard.
The recommended screening field gel test, California Mastitis Test (CMT) showing scores (2+) or (3+) proved to be bacteriologically mastitic, and thus such scores can be relied upon for dete-ction of subclinical udders, while score (1+) (46.94% agreement), require bacteriological exami-
nation.
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Direct microscopic somatic cell count revealed that all samples showed somatic cell count less than 3 x 105 cell / ml of milk were bacteriologically negative while those having count<5 x 105 cell / ml of milk wereculturally positive (100% agreement). Thus, somatic cell count. < 5 x 105 / ml of milk is an excellent tool for detection of subclinical cases.
Suggestions for mastitis control programme, herd management , milking machine management and mechanical milking procedures were discussed.