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Virginia Cooperative Extension - Knowledge for the CommonWealth

Fly control and mastitis in first lactation heifers

Dairy Pipeline: March 2004

Sue Puffenbarger
Extension Area Dairy Agent,
Franklin County
(540) 483-5161

Traditionally, heifers have been the cleanest group of animals in the milking herd. Over the last 10 years, though, the incidence of mastitis in first lactation heifers has increased by over 50%. Of those animals infected, 30% of them show Staphylococcus Aureus as the major pathogen causing infection. In the past, research has shown a link between the use of waste milk and increased mastitis in young stock. With the rising use of milk replacers we expected to see a decrease in mastitis in these animals. When this didn't happen, researchers started looking for other modes of transmission of bacteria. Recent research shows that the horn fly is a major vector of the Staph Aureus organism in livestock. Heifers can be bitten on the udder as early as one month of age and carry the Staph Aureus organism through to calving. Prevention is the key to limiting the spread of these contagious bacteria in your herd. Fly control is the number one way to do this. Fly tags alone are not sufficient. There is data to show an increasing level of resistance of flies to both the organophosphate and the pyrethrum tags. Additionally, tags do little to prevent flies from attacking udders. Pour-on insecticides offer the best solution to this problem and in addition to reducing fly populations; they provide prevention against worms and eradication of lice. Multiple summer applications of a pour on beginning in April is the key to reducing mastitis in heifers. This is the time that flies are just beginning to be active, though you may not see large numbers. All heifers, including wet calves need to be treated. Treatment needs to be repeated in June and August in order to provide maximum results. Rotation of pour-on insecticides needs to be done every other year to reduce fly resistance. If you are currently having a problem with mastitis in your first lactation animals, culture needs to be done to isolate the causative organism. Research done by Dr. Steve Nickerson from Virginia Tech has shown that you can achieve cure rates exceeding 90% for Staph Aureus if you treat heifers with a dry cow product 6 8 weeks prior to calving. There was no difference in cure rates between dry cow products used. Cure rates for these animals if treated during lactation are 50% or less. Contact your local veterinarian for recommendations on treating heifers prior to calving and for the dose of pour-on used for young calves. Staph Aureus is a major mastitis pathogen in the dairy industry. It is highly contagious, difficult or impossible to cure and causes great economic losses due to lost milk and increased somatic cell counts. Prevention of this disease in first lactation animals is the best way to control its spread and reduce its economic impact.

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