For most cows, the highest risk period for new mastitis infections will be the calving period — we consider this to be from two weeks before she calves until two weeks after she has calved.
During this stressful period, cows’ natural defence mechanisms and immunity are likely to be lower, making them more prone to new infections or a flare up of existing infections that have either carried through or developed during the dry period.
Most of the new mastitis infections in this period are likely to be environmental (commonly Strep uberis), and for this infection to occur, the teat must come into contact with contaminated material (generally mud and/or faeces), and the bacteria must be able to enter the udder through the teat canal and multiply into an infection.
The choices that were made at drying-off will impact on these risk factors, both in terms of curing existing infections and also sealing the teat canal to prevent the entry of bacteria, but there are still some key actions that will help to reduce the risk of new infections during the calving period.
Here are a few things to consider before calving comes around again.
Springing and calving cows
The amount of faecal contamination in the calving area will be a direct result of how many cows in the calving area and how long they are there.
Will you have sufficient clean areas for calving that have not been grazed for at least the previous few weeks? Start planning for these areas at least a month or so before the start of calving.
Can you minimise the number of springers in the calving area to those very close to calving, so numbers are lower and they are there for less time?
If a heifer or cow begins to drip milk as she approaches calving, the seal has been lost and she is then high risk for the entry of bacteria into the udder.
Cows on the point of calving with large, tight udders that are dripping milk should usually be brought in and milked; cows and especially heifers with udder oedema (flag) are also at a higher risk of infection.
Discuss with your vet if a treatment program for these cows is necessary.
Hygiene at the first milking
While pre-milking teat preparation is not routinely used in most Australian herds, there is now good evidence that targeted use can be of significant benefit.
Washing and drying all teats in fresh cows and heifers at the first milking achieves several goals:
- Removal of contamination from the teat surface before milking.
- The washing action stimulates much better "let down".
- Post milking teat disinfectant spray will be better able to contact bacteria on the teat surface immediately after milking.
- The emollient in the teat disinfectant will be able to get direct contact with teat skin to aid skin condition in these fresh cows and heifers with sensitive, swollen skin.
Drying teats after washing is very important, because cups going onto wet teats will likely lead to cup crawl and teat congestion; just what we don’t want in these fresh cows!
This short routine will take less than a minute for most cows, yet will result in the fresh cows milking quicker and cleaner, and will substantially reduce the risk of infection, especially in wet, muddy conditions.
If you milk fresh cows "on the bucket", then unless your dairy is already a low line, you will have "converted" it to a low line for these cows.
This means you will be milking them with a higher vacuum at the teat end than normal — often significantly higher! It is quite common for us to measure these cows milking at 4 to 6 kPa higher than normal.
Which cows would you least like to milk at a much higher vacuum than normal? The fresh cows and heifers, of course.
Two options to consider are:
- Milk these cows last without “the bucket”, after the vat has been disconnected.
- As a compromise, if you do use "the bucket", make very sure that you do not over milk these cows! Don’t go off to do other jobs while they are milking: stay close enough to remove cups as soon as they have finished milking.
On any particular farm, there are likely to be many factors that influence the risk of mastitis during the calving period, but on most farms, these simple things are likely to make a significant difference, and at an insignificant cost.
■ Rod Dyson is a veterinary surgeon and mastitis adviser at www.dairyfocus.com.au