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.
Carefully consider the disease history of cows before buying as replacements or assembling a herd from mixed-aged cows or from multiple sources.
Many outbreaks of mastitis follow the introduction of infected cows to a herd.
21.1 - Buy heifers before first calving (rather than cows), where possible
It is likely (although not certain) that a heifer that has never been in another dairy area will be free of the major bacterial causes of mastitis.
21.2 - Don’t buy cows unless bulk milk SCC and mastitis records are available
If the BMSCCs have been less than 200,000 cells/mL for the past six months, the herd of origin is likely to have contagious mastitis under control.
Don’t buy cows unless they have Individual Cow SCC records. Avoid cows with one or more SCC above 150,000 cells/ml and be wary of older cows.
If cows have received antibiotic dry cow treatment, you should know the product used and the date of treatment.
21.3 - Check cows udders before buying them, and again before milking them
Feel udders for uneven consistency or lumps. Look at teats for teat sores or damage.
If lactating, check foremilk by stripping milk, preferably onto a black surface, and definitely not onto your hand. Milk containing infection may be spread during this procedure, so gloves should always be used, and rinsed under running water between cows.
If abnormalities are detected, have a milk sample cultured. Knowing if contagious bacteria such as Staph. aureus are present allows infected cows to be managed appropriately e.g. segregated from uninfected cows, treated with antibiotic DCT at dry off. Consult your veterinarian for more advice.
See Healthy Udder - Find 1 and 3 - for more on finding clinicals and collecting samples for bacterial culture.
See Guideline 4.1 and 4.2 for information on checking udders and foremilk stripping.
21.4 - Milk introduced cows last until you are confident that they are free of mastitis
Introduced cows should be regarded as suspect mastitis cases until they have a problem-free lactation in the new herd.
Ideally they should be maintained independent of the home herd.
- Milk all newly purchased animals last or with separate equipment as a standard procedure until they have a clean bill of health
- Do not put the milk in the vat If there is any suspicion that the milk may contain antibiotic residue
- Consider taking samples for bacterial culture.
21.5 - Don’t milk other people’s cows with your herd
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.
Assembling new herds
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:
- Purchase younger cows where possible.
- Check mastitis and SCC records.
- Purchase milkiing cows where possible so that foremilk can be checked for:
- clinical signs,
- somatic cells with an Rapid Mastitis Test,
- bacteria by collection of samples for bacterial culture.
- Ensure that all purchased cows are treated with antibiotic dry cow treatment at drying off.
In an emergency In emergency situations, where neighbours need to share milking facilities, operate strict quarantine measures such as:
- Separately graze and milk herds.
- Ensure that the milking plant is washed between milking different herds.
- Ensure that antibiotic cows are kept segregated and milked at the end of each herd.