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Mastitis continues to be a disease that causes substantial economic loss on most dairies. Therefore, it’s important that herds of all sizes have a comprehensive udder health strategy in place — a strategy that includes effective prevention practices, as well as prompt identification and proper management of both clinical and subclinical mastitis cases.

Investing time and money in preventing mastitis will usually provide a substantial return by way of a reduced incidence of clinical and subclinical cases. Although there are many areas where this investment can be made, preventing mastitis in the dry period and transition period should be high on the list.

To start, it’s a good idea to see how well you’re currently doing at preventing new infections by monitoring your fresh cows and heifers. If you’re on DHIA, you can look at your first test day somatic cell count (TD01 SCC) to see what percentage of those are greater than 200,000 cells/ml (linear score 4). You should be able to have less than 10-15% of your animals with a TD01 SCC >200,000.

Another thing to monitor is the California Mastitis Test results of fresh cows and heifers. If you do a CMT at 36-48 hours after calving, you should find that less than 15-20% of your animals have a positive reaction on the test.

Lastly, monitoring what percentage of animals have a clinical case of mastitis in early lactation (up to 30 DIM) is also useful, since many of these cases originated in the dry or transition period. If less than 5% of your cows have a clinical case of mastitis in the first 30 days of lactation, you’re doing quite well, although you might be able to do even better.

Observing Udder Hygiene

Mastitis in the transition period is frequently associated with poor udder hygiene. One of the reasons this can happen is that the close-up and fresh pens are overcrowded, and/or the bedding is not being maintained properly, which means that the udders and teats of the heifers and cows get dirty.

Additionally, the keratin plug that has — hopefully — been present during the dry period, and has been preventing bacteria from getting into the udder, starts to break down during the last part of the dry period. This means that any bacteria present on the teat and teat end have a better chance of getting into the udder and establishing an infection. And if an animal is leaking colostrum/milk while in the close-up or fresh pen, this means that it is also possible for bacteria to get into the teat and udder.

Consider doing udder hygiene scoring of your transition cows to get an idea of what percentage have more than 25-30% of their udder surface covered with manure and bedding. Well-managed herds are able to consistently achieve excellent udder hygiene in the transition period — less than 5% of cows with more than 25% of the udder covered with manure/bedding.

Whether you’re milking 40 or 2,700 cows, it’s a matter of making it a priority and putting effective protocols in place to make it happen. Of course, having motivated, knowledgeable people to carry out those protocols is also extremely important.

Remember that keratin plug? In some cases it can take a long time for the plug to form, and in some cases an effective keratin plug may not be formed at all, especially in high-producing cows.

One way to mimic the function of a keratin plug is to infuse a “teat sealer” at the time of dry off. If done properly, this product will sit in the teat cistern and help to block any bacteria from entering and establishing an infection. Not all herds will benefit from using a teat sealer, but it’s certainly something worth considering if you have a high level of infections at calving or in early lactation.

There are also important nutritional, stress and other factors that can put cows at an increased risk of getting mastitis during the transition period. But ensuring that your animals have very clean udders and teats during the transition period means that the risk of getting mastitis is lower, even if they may have some of these other factors present.

Ernest Hovingh is an Extension veterinarian with Penn State.

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