Authors: K. Knappstein, G. Suhren, H.G. Walte
The prevention of antibiotic residues is an important aspect
of milk quality. Limited information is available on the influence of milking
frequencies deviating from regular milking of 2 times per day on the excretion
of antibiotic residues in milk of treated cows.
As part of workpackage 5 within the European project "Implications of the
Introduction of Automatic Milking on Dairy Farms" the excretion of antibiotic
residues in milk of healthy cows was investigated. 4 different udder injectors
containing 6 different antibiotics alone or in combination were tested. 3
groups of 5 cows were tested per drug. The experimental groups were milked
three times per day (milking interval 8 hours) respectively 1.5 times per day
(milking interval of 16 hours) and the excretion of antibiotic in cow
composite milk was compared to a reference group milked 2 times per day
(milking interval 10 and 14 hours). Different approaches for determination of
the withholding period were applied.
For three drugs tested the milking frequency had a significant influence on
the excretion period: with increasing milking frequency the excretion period
decreased. The differences were significant between groups milked 3 times and
1.5 times per day for all components of these three drugs. For one drug
containing ampicillin and colistin the excretion period was not influenced by
the milking frequency. Milk yield, somatic cell count and days of lactation
had no significant influence on excretion of any antibiotic substance. The
lactation number influenced the excretion time of cefquinome as well as of
penicillin and dihydrostreptomycin in a combined drug, but for latter two
drugs this effect was related to body weight.
Commercially available microbial inhibitor tests applied as screening methods
for detection of antibiotic residues in milk detected penicillin G, ampicillin
and nafcillin at concentrations below or at Maximum Residue Levels (MRL),
whereas sensitivity for detection of cefquinome, dihydrostreptomycin and
colistin was insufficient. In a second part of the investigation the excretion
time of antibiotic residues in milk of cows treated for clinical mastitis was
determined. The results of that part will be presented in deliverable D12.
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© Animal Sciences Group -
Wageningen UR. Last update:
20-02-2008 10:03. |
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