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| Author(s): |
Ana Carolina de Oliveira Rodrigues
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2008-04-15 |
| Examining board members: |
Paulo Fernando Machado;
Maria Aparecida Vasconcelos Paiva e Brito;
Hélio Langoni;
Alice Maria Melville Paiva Della Libera;
Silvio Sandoval Zocchi
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| Advisor: | Paulo Fernando Machado |
| Abstract | |
The present thesis investigated the diagnosis and treatment of bovine mastitis by using a simple test for somatic cell count, on-farm bacteriological culture and guided treatment protocols. To rapidly determine SCC, Somaticell® test was used on milk samples having the results compared to electronic count and evaluated by sample type and reader. The Somaticell test correctly determined the SCC in fresh milk samples of mammary quarters. The correlation between Somaticell and electronic SCC was 0.92, being kappa coefficient equals to 0.82. This test presented good reliability to determine intramammary infections using a threshold of 205.000 cells/mL (sensitivity = 91.3% and specificity = 96.0%) and showed greater SCC in samples containing major mastitis pathogens. Minor intra-individual variation was detected when performing the test. Probably, the homogenization procedure of the test is the most likely explanation for the observed variation. However, the final analysis indicated that this variation was not significant and did not affect the amount of samples classified as having subclinical mastitis. Milk samples preserved at 4 ºC up to 5 hours did not change test results. Nevertheless, frozen or bronopol preserved samples were not suitable for this test. Clinical mastitis data indicated that infections caused by Gram positive bacteria were mainly seen on clinical cases with visual milk abnormalities and udder edema of clinical recurrent animals showing monthly average SCC greater than 200,000 cells/mL. In contrast, clinical mastitis caused by Gram negative bacteria was frequently associated with systemic signs in high producing cows. In addition, mastitic samples without bacterial growth in the laboratory did not present a defined pattern in relation to mastitis grade and animal characteristic. The on-farm bacteriological culture using Azide Blood Agar Base, MacConkey Agar and Vogel-Johnson Agar, showed adequate recovery of mastitis causing pathogens. In 79.3% of the cultures (n = 203) the on-farm results agreed with the standard laboratory culture. Interestingly, the concordance rate was affected by the number of colony forming units in the milk sample. The sensitivity and specificity of on-farm culture were 83.0 and 76.5%, respectively. These results were positively influenced by growth of Gram positive bacteria and negatively influenced by growth of Gram negative bacteria and samples with no growth. The use of fresh milk samples in on-farm culture seemed advantageous for bacterial recovery, although premature plate reading of bacterial growth and simplicity of this methodology might reduce its accuracy. Mastitis treatment guided by on-farm culture showed an overall bacteriological cure rate of 69.7%. In the majority of quarters, SCC remained elevated within 21 days after detection of clinical mastitis. Gram negative bacteria presented greater cure rates. On the contrary, Staphylococcus aureus mastitis displayed the lowest cure rate even by using extended antibiotic treatment. Intramammary antibiotic treatment did not show effect on cure rates of grade 1 and 2 clinical mastitis caused by Gram negative bacteria or with negative growth in the on-farm culture. (AU) | |