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| Author(s): |
Roberto Bellizia Raia Junior
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2001-08-28 |
| Examining board members: |
Elizabeth Oliveira da Costa Freitas Guimarães;
Hélio Langoni;
Elizabeth de Souza Nascimento
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| Advisor: | Elizabeth Oliveira da Costa Freitas Guimarães |
| Abstract | |
The presence of antimicrobial residues im milk is a public health concern, because they may cause allergic reactions and may lead to the development of resistance to antimicrobial agents by bacterial strains. It is also an economic problem because it interferes with starter cultures used in dairy products. Mastitis, the inflammatory process of the mammary gla nd, is the main reason to treat dairy cows with antimicrobial agents. The purpose of this study was to verify the influence of mastitis on the withdrawal period of several intramammary and parenteral antimicrobial agents used in lactating cows, as well as to evaluate the presence of detectable antimicrobial residues in bulk tank milk, in relation to the mastitis rates among the studied dairy farms. A total of 60 bulk tank samples of dairy farms and 135 individual samples of healthy and mastitic dairy cows were screened to verify the occurrence of antimicrobial residues with a microbiologic test (Delvotest®). A correlation was detected between antimicrobial residues in bulk tank and high clinical mastitis rates (r= 1.0; Spearman\'s test). A higher withdrawal period, exceeding that determined by the manufacturer, was observed in the milk of mammary glands presenting inflammatory processes, both in animals treated by the parenteral route, and those treated by the intramammary route. This observation ranged from 11 to 60% of the analyzed samples and was verified in all groups treated with different antimicrobial agents (betalactam, aminoglycosides, tetracycline and sulfas). Statistically significant difference was detected (p<0.05, Fisher\'s test) at seventy two hours after the parenteral treatment in samples from animals presenting inflammatory processes, in relation to samples from animals that did not present mastitis. That is, there was a higher withdrawal period in the samples from animals presenting mastitis. In the evaluation of the influence of inflammatory reaction natural inhibitors on Delvotest®, it was verified that 33% of the samples from clinical mastitis quarters and 18% from subclinical mastitis quarters were positive, and that quarter samples without inflammatory processes were negative. These differences were statistically significant (p<0.05, Fisher\'s test). Among the main onclusions, it should be pointed out that there was a correlation between high clinical mastitis rates in the dairy herd and antimicrobial residues in bulk tank milk. Another important result was that mammary glands presenting inflammatory processes exhibited higher withdrawal periods when compared with mammary glands that did not present inflammatory processes, and that sometimes this withdrawal period exceeded the period recommended by the manufacturer. It was also observed that milk samples from untreated animals, when tested without preliminary heating at 80ºC, were positive, due to the occurrence of natural inhibitors produced by the inflammatory process, showing their interference on microbiologic tests. Therefore, it was demonstrated that previous heating is helpful to avoid false positive results when microbiologic tests are used to detect antimicrobial agents residues in milk samples. As an overall conclusion, it was well demonstrated that mastitis interferes in antimicrobial residues in milk. (AU) | |