Prevention Is Key to Mastitis Control in Sheep

By Sarah Watson, Livestock Editor
Thursday, March 15, 2007 12:33 PM CDT

Although most research conducted has focused on mastitis control in dairy cattle, mastitis does exist in the sheep industry, and is a large cost for producers.

If producers know the enemy, what is causing the mastitis, then they are able to better prepare for 'germ warfare', said Leo Timms, Iowa State University Extension dairy science specialist during the Sheep Management WISLINE program series conference call last week.

"If you're not looking for mastitis in your herd, you've missed the boat," he said.

Mastitis is an inflammation of the mammary gland, and is caused by a reaction to tissue injury.

The inflammation can result in redness, swelling, heat, pain and a loss of mammary function.

There are different types of mastitis including clinical, chronic and subclinical. In clinical mastitis visual abnormalities can be found in the milk, udder or lamb. They include fever, loss of appetite and sometimes death.

Chronic mastitis lasts for a longer duration with variable signs. Subclinical infection, "the silent one," has no visible signs and results in loss of function. Special tests are needed to confirm subclinical mastitis infections.

"This type is the silent one," he explained. "Sometimes we can't see it."

The types of mastitis can be linked to the germ causing the infection, and knowing the enemy allows producers to fight the infection more efficiently.

"If you know characteristics, you know how to win the battle," he said, adding that knowing the strengths and weaknesses of the agent causing the infection is the best way to prevent and find the correct treatment.

Pasturella, a commonly found in the lung, is a bacteria that can cause mastitis.

"They're sleepers," he said. "They wait for an opportunity."

Pasturella usually causes mastitis when a ewe is under a lot of stress, like during lambing. The bacteria get into the blood stream and gets in the milk. Once in the milk they grow and shed continuously.

"Once they're in milk they're a monster," he said. "They're much harder to treat."

Another cause of mastitis is Staphylococcus aureus. Staph is usually associated with a chronic infection.

"Staph is a wound invader. It's a scary bug," he said. "It drops milk production immensely."

In a commercial milking operation it is spread easily.

As a wound invader, it is important to keep the teats clean and healthy.

"Keeping teat ends healthy is probably the single most important thing we can do," he explained. Cold weather has the potential to cause the teat to crack. The staph will then enter through the opening to cause the infection.

Environmental agents that cause mastitis include some Strep species and E. coli (coliforms).

"The bottom line is they're from the environment," he said. "They're going to come out of the bedding."

Like Staph, Strep species are opportunistic, and become problems during stressful times for ewes.

"You find a lot around lambing time," he said.

Unlike the other infection agents, coliforms don't stick to skin. They need water to survive.

If the culprit of mastitis infection is coliforms, then producers should look at the bedding. Clean dry bedding will help prevent coliform infections.

Along with knowing the enemy, protecting ewes during their highest risk times is crucial.

Most mastitis is contracted during two periods; the first few weeks post weaning, and two weeks pre-lambing to a few days after lambing.

Iowa State research has shown over 50 percent of new infections occur during these periods.

"Lambing is the big time," he said. That's the time when the animal goes clinical."

Lambing leads to a decrease in immunity and makes the ewes more susceptible to infection.

New infections occur because the increased milk accumulation serves as a great feeding ground for the bacteria, and as the mammary pressure increases teats can shorten and open allowing for bacterial entrance.

"It's like having a cafeteria," he said about the nutrient rich milk availability to the bacteria.

Aiding to the problem is a lack of nursing or flushing, and the white blood cells that normally fight infection are preoccupied by eating the milkfat and protein.

Once a ewe is infected it is important to try detecting it as early as possible. Looking for clinical signs in the ewe, lamb, udder and possibly milk is important.

Timms said there is no better detection method than eyes and hands. Unthriftiness and weight loss in lambs should signal the need for an examination of the ewe's milk.

Taking temperatures is also a good way to tell if "something" is happening.

Udder palpitation following weaning, prior to breeding and at lambing should be conducted to check for chronic mastitis.

Infections occurring at the subclinical level need to have testing preformed.

One easy and cost-effective on-site test is a CMT (California Mastitis Test), which evaluates white blood cells in the milk.

"In my book this is your most powerful tool," he said.

In the CMT test, the milk reacts with a solution to determine the amount of white blood cells present in the milk. If a high number of white blood cells are found, the mixture of milk and solution will gel.

For the test to be useful to the producer, they need to determine the amount of white blood cells that need to be present before they feel the infection is a problem. The test is ranked on a scale of 0 to 3, 0 having no gelling effect and 3 like grape jelly.

"If you're at 5 million or 500,000 it tells you the same thing," he said. It means there is an increase in white blood cells and a reason for it.

"Maybe the easiest way is if it gels or it doesn't," he said. "The CMT becomes an awareness tool for you."

The CMT can act as a guide for the producer.

"The CMT can be your screening tool," he explained. "If you don't get a reaction, you're almost 100 percent sure she's not infected."

Monitoring the flock and looking for signs is a must, he said. This allows producers to minimize the number of new infections and eliminate existing infections.

Understanding the organisms involved and how they infect the animal allows producers to create environments where the ewe strives, not the bacteria.

The goal is to maximize immunity and teat end integrity, while minimizing the exposure to bacteria. Keeping the animals clean, dry and comfortable will help producers reach that goal. If the animals are comfortable they aren't concentrating on other things, he said.

"Try to minimize moisture and how things can grow," he said. That's the critical part."

Using teat treatments could also help decrease susceptibility during high-risk periods.

Providing the ewes a nutritional diet will maximize immunity. Providing creep feed for lambs is also important, but Timms warns that creep feeding is not a substitute for mastitis management.

Eliminating existing infections will help improve health. There are three ways to cure existing infections. The first is spontaneous cure. Over 50 percent of infections will be cured through the ewe's immune system.

The second cure is culling the animal. Decreased lamb performance along with signs of mastitis including lesions and elevated CMT scores should be considered before culling.

The third option is treatment. Treatments can be administered through lactation therapy, dry treatment at weaning, and pre-lambing treatment and therapy.

During lactation, early diagnosis and detection is crucial. Keeping ewes on good feed and water, along with keeping the ewe milked out or lamb nursing is important.

Timms suggested working with the veterinarian to determine appropriate treatments and protocols.

At weaning, producers need to cure existing infections, and prevent more infections from occurring.

Flocks with lactation mastitis problems or individual problem ewes are prime candidates for dry treatments.

Dry cow tubes and injectables are treatments that can be used during the dry period. Sanitation is a must when using dry treatments. Producers should use partial insertion, not full, when using dry period treatments.

Pre-lambing treatments need to be discussed with the veterinarian. Producers should avoid opening the teat unless absolutely necessary.

"I don't like tubes," he said. "It's a reasonably sterile environment. I'm not sure you will get a great response."

Timms encouraged producers to concentrate on prevention and not treatment. "Therapy is a last resort," he said.

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