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Is paratuberculosis in dairy cows harmful to milk?

Posted on: December 7, 2019, by Eleanor

The paratuberculosis of dairy cows is an epidemic that can cause significant economic losses. Strict control and extermination measures are needed to prevent its spread. The incubation period varies from 6 months to more than 15 years. Therefore, after dairy cattle were infected with paratuberculosis, there were no clinical symptoms in a certain period. Most of the symptoms occurred only when the body was weak after calving, and the incidence of the disease was the highest in cows aged 3 to 5 years.

Especially when cows begin to conceive, give birth and lactation, they are prone to clinical symptoms. Therefore, under the same conditions, the disease is much less common in bull cows and castrates than in female cows; the symptoms of high-yielding cows are more serious than those of low-yielding cows. The lack of inorganic salt in the feed may promote the development of the disease. Dairy cows infected with paratuberculosis should be detected in time, eliminated as early as possible and take corresponding preventive measures.

1. Symptoms of paratuberculosis in dairy cows

The early symptoms of this disease are intermittent diarrhea symptoms with normal body temperature, which is difficult to distinguish from other diarrheal diseases in clinical symptoms. After symptomatic treatment or pregnancy, symptoms can be controlled for a short time, but when confronted with stress reactions such as calving, drastic climate change, and changes in forage feed, clinical symptoms will appear immediately and recur several times.

After that, it became obstinate diarrhea. The intermittent diarrhea of 2-3 weeks quickly deteriorated into persistent diarrhea. The feces of diarrhea contained obvious blood, air bubbles, mucus, and foul odor. The severe cases were jet-like diarrhea and were no longer sensitive to drug treatment. Symptoms also gradually worsened, with hair discoloration and edema in the lower jaw and abdomen. Common edema in mandibular and thoracic lobes, hair loss, slow weight gain, and significant wasting, decreased lactation volume and milk quality or stopped lactation, prolonged empty period. Eyeball subsidence, a certain degree of appetite, loss of appetite, or even waste, do not like to eat concentrates, severe weight loss to "skin and bones", intermittent fever, muscle atrophy, tears, and blood potassium red blood, blood calcium, leukopenia, anemia and other symptoms. Finally, you can't stand without eating. The mortality rate of the infected population can reach 10% annually.

2. Prevention of Paratuberculosis in Dairy Cows

The focus of this disease is prevention. When importing dairy cows, the paratuberculosis quarantine should be carried out to confirm that it can be introduced after health. The infected cows should be detected in time, eliminated in time, and vaccinated newborn cow babies.

In dairy farms, all dairy cows should be quarantined to eliminate infected cows in time. Early symptoms are not very obvious and easy to be confused with other diarrhea diseases. Therefore, laboratory diagnosis should be combined with clinical symptoms to make a timely diagnosis. To facilitate the detection of diseased animals, cattle farmers should early disposal of them, so that the bacteria discharged from them do not infect other healthy cattle. Therefore, paratuberculosis immunization should be carried out at least twice a year for all dairy cows. At present, there are two main detection methods, bacteriological diagnosis, and allergic diagnosis. The most commonly used diagnosis method is an allergic diagnosis.

(1) Material: shearing scissors, vernier calipers, 5 ml syringes and needles, 75% alcohol cotton balls, record books, etc.
(2) Drugs: Paratuberculin, manufactured by China Veterinary Drug Supervision Institute.
(3) Method of operation: Number the animal to be inspected, cut the skin in the middle of 1/3 of the neck, about 10 cm in diameter, measure the thickness of the original skin with a caliper, and record it, disinfect it with alcohol cotton ball locally.

Dilute Paratuberculin into 0.5 mg/ml sterile water for injection and 0.1 ml intradermal injection. If subcutaneous injection or overflow occurs, an additional injection should be given at a distance of 8 cm from the original injection point.

(4)Result Judgment: 72 hours after injection, the reaction was observed, the inflammation of heat, swelling, and pain was examined, and the skin thickness of the injection site was measured by caliper.

(5) Negative reaction: Delayed allergic reaction time or inflammatory reaction at the injection site was not obvious, skin thickness difference was less than 2.0 mm.

(6) Positive reaction: local inflammatory reaction, skin thickness difference (> 2mm) is positive; local inflammatory reaction is not obvious, skin thickness difference 2.1-3.9mm, can be re-examined after 3 months according to the situation, the same operation is performed in the corresponding parts of the injection site, 72 hours later, the skin thickness difference (> 2mm) is still positive, should be eliminated immediately.

If the possibility of tuberculosis infection is considered, the allergic reaction test of tuberculin can be done on the other side of the neck of the paratuberculosis allergic reaction. After 72 hours, the results show that the side of the allergic reaction with larger skin difference is the epidemic disease of diseased cattle, that is, the side of the neck of the paratuberculosis allergic reaction with larger skin difference is paratuberculosis.

Once the paratuberculosis dairy cows are quarantined, they should be eliminated in time, and thorough sanitary disinfection should be carried out on the spot and the cow dung, cowshed, feeding trough, utensils, and sports ground.

3. Preventive measures

(1) Calf vaccination

Diagnosis and comprehensive prevention of paratuberculosis in dairy cows
Diagnosis and comprehensive prevention of paratuberculosis in dairy cows

(2) In addition to the above preventive measures, the following supplementary measures should be taken: strengthening feeding management, enhancing resistance, especially giving adequate nutrition facts to young cattle; carrying out fecal bacterial examination on suspected animals; cleaning up livestock houses in time; separating calves from diseased cows immediately after delivery and keeping them in isolation; and not feeding diseased cows'milk. Feed healthy milk or sterilized milk.

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