Control external parasites to maintain cow comfort

St. Joseph, MO, Nov. 2, 2012 — In the dairy industry, cow comfort plays an important role in animal health and milk production. Interference with feed intake or resting time is reflected in lost milk production. One management practice that producers can utilize to help maintain cow comfort within their herd is to control irritating external parasites such as lice and mange.

Clinical signs of mange are the development of crusty asbestos-like lesions near the tail head, caudal udder and inner thighs. These lesions cause intense itching and restlessness, leading to decreased cow comfort and milk loss. Lice clinical signs include intense itching and hair loss. The greater the percentage of animals with clinically apparent lesions within a herd, the greater the herd milk production losses.

Dr. Brian Miller, Professional Services Veterinarian for Boehringer Ingelheim Vetmedica, Inc., says the best way to avoid costly external parasite populations is to complete a whole-herd pour in late fall or early winter. In northern climates, this is typically mid-November.

"Since lice and mange populations peak in January and February, we recommend a whole-herd pour in late fall," says Dr. Miller. "Because lice and mange spread by direct contact, treating all animals within the herd at the same time creates a baseline and stops the spread of these parasites."

Dr. Miller recommends producers include the following steps when developing a whole-herd external-parasite control program:

  • Complete a whole-herd pour annually. Being proactive and treating the entire herd is the best way to eliminate the risk for a lice and mange outbreak. Treat all cattle within a herd, not just those showing obvious clinical signs. Late fall is the ideal time to treat the herd.
  • Dose properly. Incorrect dosing is the number one reason pour-on programs fail. Proper dosing depends on the weight of the animal, so be prepared to reset the applicator gun as needed to ensure each animal receives the appropriate dose of pour-on.
  • Apply properly. A proper application includes pouring along the back of the animal from the withers to the tail head.
  • Pour new additions. As new animals join the adult herd, they should be poured upon arrival. This would include springer replacement heifers or new animal purchases including bulls as these animals may have been exposed to mange and lice, putting the entire herd at risk of reintroducing external parasites.
  • Re-pour as needed. Animals that are the most severely infected with lice and mange at the time of the whole-herd pour should be re-poured three weeks later for optimal control.

Dr. Miller adds, "In addition to providing external parasite control, replacement heifers that have been pastured may also be harboring internal parasites which can negatively affect feed conversion, growth rates and milk production. Strategic deworming upon arrival rids these animals of harmful internal parasite populations as well."

For more information on developing an external parasite control plan, consult your veterinarian or Boehringer Ingelheim Vetmedica, Inc. representative, or visit



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