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Moving animals on and off a farm has its risks. A common way for cow-associated mastitis bacteria to be introduced into a herd is in the udders of cows that are brought in. These bacteria can spread rapidly through a herd, so it is better not to introduce them in the first place.
Replacement cows may be purchased to increase the size of the herd, to assemble a new herd, or to maintain cow numbers after culling. One of the most common ways of introducing the cow-associated mastitis bacteria into a herd is in the udders of cows that are brought in. Bacteria such as Staph. aureus and Strep. agalactiae can spread rapidly through a herd. It is better not to introduce the bacteria in the first place.
You should carefully consider the disease history of cows before buying as replacements or assembling a herd from mixed-age cows or from multiple sources.
Buy heifers before first calving (rather than cows), where possible
Don’t buy cows unless bulk milk SCC and mastitis records are available
Check cows udders before buying them, and again before milking them
Milk introduced cows last until you are confident that they are free of mastitis
The risk of introducing mastitis by sharing milking facilities with cows from other herds is high. This includes temporarily milking 'carry over' cows for neighbours or sending cows away from your herd to be milked for a temporary period. To avoid costly mistakes it is best to maintain a closed herd at all times.
Cows that enter a herd are a potential source of mastitis pathogens, acting as a source of infection and potentially increasing your bulk milk SCC. Practical precautions include:
In emergency situations, where neighbours need to share milking facilities, operate strict quarantine measures such as:
Cows sold for slaughter from our dairy herds must be free from all unacceptable residues. To avoid errors, all cows treated with antibiotics must be identified.
Markings usually remain visible for the duration of the milk withholding period, but not for the full length of the meat withholding period. You must use permanent identification systems and written records to check when meat withholding periods have expired.
Keep records of all treatments and checking these for every cow before she is sold. Not selling meat unless the antibiotic withholding period for meat has passed.
For more information see Selling cows Guideline 20 and Technote 20