AMES, Iowa — It is not unusual for dairy goat farmers to be thinking about drying off their herd this time of the year. Dr. Michelle Buckley from Iowa State University spoke during a webinar this month in which she talked about the process of drying off dairy goats and treating them for mastitis.
Buckley shared information ranging from the natural defenses goats have to the treatments we can give them to bring them back to health.
“We are not milking (goats) during the early dry period, obviously, so we are not removing any bacteria that may have gained entry,” Buckley said. “After dry-off, a keratin plug forms to provide a long-term barrier.”
The time period between the last milking and the formation of the keratin plug, which changes from animal to animal, is when the mammary gland is most vulnerable. However, it is not the only time mastitis can form. During the webinar, Buckley focused on subclinical mastitis.
There are different ways, Buckley said, to detect subclinical mastitis. She described how it visually cannot be detected but rather needs to be detected through a culture, California mastitis test or by directly tracking somatic cell count.
Doing a culture has another benefit; it can tell what bacteria is causing the infection of the udder. The most common bacteria found is non-aureus staph, which has many different strains within itself, the most common being epidermidis. Once a goat has mastitis, there are many ways it can affect them. During her webinar, Buckley shared studies that explain these ways.
One study showed there was no change in the milk yield throughout the first lactation, but it did note there could be a “slow burn effect.”
“They are seeing that atrophy of the functional mammary tissue might take more than one lactation,” Buckley said. “Or, they might not see the effects fully until they’ve looked for a couple of years.”
Every study from a different country resulted in different results, likely due to the mastitis cases being caused by varying bacteria. Even SCC results were different across the studies. In some studies, SCC increased, and in others, it decreased. The differences in SCC, Buckley said, are caused by how well various goats do in adding water to the milk within their udder to flush the bacteria out.
While some goats are able to cure themselves, most need an added boost. There are two different ways Buckley discussed as to how mastitis can be treated. One of the ways is during lactation. For a couple days, a short-acting intramammary antibiotic is injected into the infected halves. This type of treatment averages a 53% cure rate. If left untreated, the cure rate is only 12%.
Another form of treatment Buckley described was dry treatment. This consists of infusing a long-lasting antibiotic into the udder after the doe has been dried off. Benefits of this treatment include a higher chance of killing the deep-rooted infections, only needing to do the treatment once and a cure rate over 80% on average.
The downfalls of this treatment are the limited windows for lactation, having to know the kidding date and dry period length, the withdrawal period after freshening, and the cost of the treatment.
However, if mastitis is left untreated, it has many impacts on the herd. One is the longevity of the herd. While a study addressing longevity after mastitis has not been completed on goats, a study conducted on sheep showed that there was an increase in the number of animals that were culled because their SCC was greater than 1,000,000.
This led to the need to treat the animals but not compromise the milk quality. During the webinar, Buckley said knowing the breeding dates, keeping track of which animals were treated and following the withhold period are important steps in keeping the milk quality from dropping.
“(The goats) should all have a permanent ID, like a tattoo, as well as a temporary identification, like a leg band,” Buckley said. “It’s also best if we can separate the treated does in a different pen.”
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