الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 212 |  |  |
| | | from | 212 | | |
Abstract
6. Even with the advanced technology and improved hygiene systems of dairy farms, SCM which yields no visible clinical signs or milk abnormalities is still one of the most prevalent production disease causing severe economic losses in the dairy herds. So the present study was done to throw some light towards the different applicable screening tests used for earlier detection of sub clinically infected quarters as an aid in early diagnosis and treatment of affected dairy animals.
After results collection of different screening tests of SCM, multiple correlations were studied to reach deep understanding and trust of each test what will aid the early diagnosis of SCM. Then regular BTM samples were collected analyzed and all results were correlated.
Examination of total number of 298 cows using CMT revealed 18 (6.04 %) cows had clinical mastitis while 280 (93.96 %) cows were apparently normal of which 196 (65.77 %) were positive CMT while 84 (28.18%) were negative.
Out of 1093QMS, 493QMS had SCM in (45.1 %); that are reacted positively with CMT. Of which7.41 %, 21.32% and 16.37 % had scores (+), (++) and (+++), respectively.
Average SCC in negative CMT examined QMSs was 148×103 cell/ml while the average SCC in positive CMT samples scores +, ++ and +++ were 278×103, 457×103 and 866×103 cell/ml, respectively.
The correlation between CMT scores; (0; negative), (+), (++) and (+++), and SCC of the examined QMSs revealed that samples with SCC less than 250 x103 cells/ml had CMT results as 52.06%, 2.84%, 0.73% and 0%, respectively. Meanwhile, samples with SCC in the range between 250x103 - 500 x103 cells/ml had CMT results as 2.84%, 4.03%, 14.36% and 1.19%, respectively. On the other hand, samples had SCC range between 500x103-1000x103cells/ml had CMT results as 0, 0.55 %, 5.22 % and 9.15 %, respectively. Finally, only 2 CMT scores were exceeded the SCC of one million which were (++) and (+++) with a percentages of 1% and 6.04 %, respectively.
Regarding milk scanning and it`s correlation with SCM, all milk compositions synthesized in the glandular tissue of the mammary gland are gradually decreased by increasing the severity and degree of SCM while other milk compositions that come ready from the blood are slightly increased by the effect of inflammation and edema. Thus, these parameters can hardly use in the diagnosis of SCM.
Regarding isolation and identification of bacterial causes of SCM in examined dairy cows, Staphylococcus species were the most prevalent isolates; 433isolates (87.83%) of which S. aureus was the most predominant (237 isolates; 48.07). Meanwhile, CNS were recovered from 196 samples (39.76%). Antimicrobial sensitivity testing revealed high resistance of S. aureus and CNS isolates to ampicillin and cefoxitin.
PCR was applied on 10 phenotypically methicillin resistant S. aureus isolates for detection of 2 genes; virulence gene (hlg) and methicillin resistance genes (mecA). The mecA gene was found in 40% of isolates while hlg gene was not detected in any isolate.
Streptococci were recovered from 275 samples (55.78%) of which no isolate were identified as S. agalactiae. Moreover, E. coli were recovered from 245 QMS (49.7 %). PCR was applied on 10 E. coli isolates for detection of 2 adhesin genes fimH and tsh. The fimH gene was found in 80% of isolates while tsh gene was detected in 50%.
The overall prevalences of bacterial isolation revealed bacterial isolation from a total of 447 samples (90.7%) of which 131 samples (26.6%) showed single isolates while 316 samples (64.1%) showed mixed isolates.
Regarding single infections, S. aureus was the most prevalent bacteria single isolate as it was represented in 53 samples (10.75%) followed by CNS; 38 samples (7.71%). Then, E. coli and Streptococci found in 26 (5.3%) and 14 samples (2.84%), respectively.
Meanwhile in mixed infections, the highest prevalence was S. aureus+ E. coli+ Streptococci; 60 samples (12.17%) followed by mixed CNS+ E. coli+ Streptococci (49 samples; 9.94%) and S. aureus+ Streptococci (43 samples; 8.72%).
The correlation between bacterial infections and CMT scores showed that score ++ was the most prevalent recorded in a 233 cases (47.26%) of which 215 cases (43.61%) were associated with positive bacterial isolation while 18 cases (3.65%) were negative. Then, score +++ recorded in 179 cases (36.31%) of which 170 cases (34.48%) were associated with positive bacterial isolation while 9 cases (1.83%) were negative. Finally, score + which was recorded in 81 cases (16.43%) of which 62 cases (12.58%) were associated with positive bacterial isolation while 19 cases (3.85%) were negative. S. aureus had the highest prevalence in score +++ CMT while E. coli and CNS had the highest prevalence % in score + CMT.
The correlation between SCC and the microbiological analysis showed that S. aureus had the highest SCC in each CMT score while other bacteria gave lower SCC.
BTM analysis is now widely accepted as a useful tool for evaluating milk quality and monitoring udder-health status in dairy herds. Therefore, BTM were investigated for separate random farms detecting aerobic plate count, coli form count, total Staphylococci count, SCC investigation and microbial analysis of BTM samples. One or more of these tests can give good picture about the healthy status of dairy cows and to which extent this farm is committed to the hygienic standard practice.
The incidences of E. coli, S. aureus, Streptococcus species and CNS were 80%, 48%, 60% and 44%, respectively. The high incidence of E. coli contamination in BTM samples were influenced by the bad hygiene of housing and milking environment, milking cows, hygiene of milkers, cleaning and sanitation of utensils and equipment and generally bad hygienic practice in the farms.