Automatic milking
Workpackage 5: Prevention of antibiotic residues
Antibiotic residues are unwanted in products for human
consumption and may cause problems during dairy processing. When milk is
found to be positive for (bacterial) growth inhibitors, i.e. contains
antibiotic components, farmers in several countries are severely penalised.
An important measure of prevention is the withdrawal time of milk after a
cow has been treated (most frequently against mastitis) with antibiotics,
either intramammary or systemically. Each antibiotic formula has a
specific withdrawal time, based upon the maximum residue level. However,
under practical circumstances the excretion period of antibiotic residues
may differ from the withdrawal period indicated. This being the case with
conventional milking systems with more or less regular milking intervals,
there is a complete lack of information on the adequacy of the indicated
withdrawal periods in a situation with more frequent milking and with
irregular intervals as in automatic milking.
The excretion characteristics of antibiotic residues in
milk after treatment of healthy cows milked with different milking
frequencies and intervals will be determined under experimental
conditions. Additionally, the excretion of antibiotic residues will be
studied in cows with naturally occurring clinical mastitis and milked in
an automatic milking system. The detection of residues will be based on
maximum residue limits fixed by EU-regulations for health protection of
consumers. Results will lead to recommendations for management of
antibiotic treatment of cows in automatic milking systems.
Subpackage 1: Investigation of excretion of
antibiotic residues in milk under experimental conditions.
Methodology and study materials
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The excretion of antibiotic residues in milk will be
determined in cows with different milking frequencies and intervals. Four
different commercially available antibiotic formulas for treatment of
mastitis will be selected according to their use in European countries,
mode of application and application in body compartments. Three groups of
cows will be treated per formula. Each group consists of 5 cows with
comparable milk production level, number and stage of lactation. The
control group will be milked at ordinary milking times (milking intervals
10 and 14 h). Two experimental groups will be milked with higher milking
frequency (three times daily/milking interval 8 h) and with irregular
milking intervals, respectively. If prolonged excretion is suspected
milking intervals will be adapted for the following experiments. Milk will
be sampled at every milking during a period exceeding the withholding
period for at least two days. Existing microbiological (e.g. brilliant
black reduction-test) and/or immunological (e.g. radioimmunoassay)/chemico-physical
(HPLC) methods will be applied for qualitative and
quantitative/semi-quantitative detection of antibiotic residues at MRL-level.
Subpackage 2: Excretion of antibiotic residues in
milk when using an automatic milking system.
Methodology and study materials
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Excretion characteristics of antibiotic residues in
clinically diseased cows milked by an automatic milking system will be
determined. Cows with naturally occurring mastitis will be treated with
antibiotics and milked automatically in the system. Milk samples of every
milking will be collected by an automatic sampling device provided by
partner 10 and stored frozen until determination of antibiotic residues.
Detection of antibiotic residues will be correlated with data on milking
frequencies and milk yield obtained by the system.
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