ST. JOSEPH, Missouri-- When it comes to maintaining a healthy udder, the dairy cow's immune system doesn't get the attention it deserves, a panel of experts told a special session of the National Mastitis Council annual meeting earlier this year. The often complex, highly coordinated immune response to infection can easily get derailed by stress, poor nutrition, the normal hormonal changes accompanying calving and other factors, said University of Tennessee Associate Professor of Animal Science Gina Pighetti. And unfortunately, vaccines capable of completely preventing mastitis have for the most part been unsuccessful, Dr. Pighetti, a specialist in bovine immunology, told the "Opportunities and Challenges to Immune Competence" session.
Immunization is a real juggling act. "Effective vaccines require an antigen specific to the pathogen which induces an immune response, an adjuvant which amplifies and helps direct the immune response, and a delivery system to maximize the immune response," she said.
A good illustration of that reality occurs with Staphylococcus aureus bacteria--an important infectious cause of bovine mastitis cases, says Dr. Craig Jones, Associate Director or Technical Services for Boehringer Ingelheim Vetmedica. Despite producers' widespread attempts at controlling infection using dry-cow and pregnant heifer antimicrobial therapy, it's generally recognized by researchers that antibiotics aren't particularly effective once S. aureus infections get established in deep mammary-gland tissue. Therefore, Dr. Jones says, properly vaccinating heifers early and continuing to booster every six months is an important tool in prevention and control of S. aureus mastitis.
"We know that immunization against S. aurus infection can certainly be beneficial," Dr. Jones says. "However, that immunization has to start early. It has to be established before the challenge occurs and the numerous nutritional, disease, genetic, management and environmental stressors start taking their toll."
As illustration, Dr. Jones cites a study conducted by the head of University of Georgia's Animal and Dairy Science Department, Dr. Steve Nickerson, reported at last year's NMC annual meeting.
In that study, conducted at the James River Correctional Center dairy, a large Virginia institutional dairy with a 22,000-pound rolling herd average and an average somatic cell count of about 200,000, Dr. Nickerson and colleagues enrolled 106 heifers, aged 6 to 18 months, over a two-year period. S. aureus was known to be present in the herd: Previous cultures of pregnant heifers showed more than one in three were infected. Dr. Nickerson compared the results of 53 heifers vaccinated with Boehringer Ingelheim Vetmedica's Lysigin® S. aurus bacterin against an equal number of non-vaccinated control heifers.
The vaccinated group was boostered 14 days following the initial vaccination and then at six month intervals through calving. Mammary secretions were collected from each quarter at two-month intervals after calving and milk samples were collected during the first week following calving. Milk samples were cultured for bacteria and somatic cell counts determined.
Results of effective immunization against S. aurus included:
Health records kept by the dairy showed vaccination reduced the percentage of heifers that were culled or died during the trial by about one-third-down to 16.9 percent for vaccinates compared to 24.5 percent for controls.
Vaccinated heifers were in milk 13 days longer than unvaccinated controls-349 days vs. 336, respectively.
The 305-day milk yield showed vaccinated heifers produced 1,968 pounds more milk (24,928 vs. 22,960 pounds)-an 8.6 percent increase.
The actual 305-day production of fat and protein was also greater in vaccinated heifers compared to non-vaccinated heifers.
Somatic cell counts in milk samples collected during first week of lactation were cut in half for vaccinated animals.
New intramammary infections were reduced by 60.9 percent for vaccinated heifers, indicating vaccination can be useful in controlling spread of the pathogen within a herd.
The James River study agreed with results of another study led by Dr. Nickerson in 1999, which showed a 44.7 percent reduction in new intramammary S. aureus infections and about a 50 percent reduction in SCC at freshening for Jersey heifers vaccinated with Lysigin. At $12 milk, the James River study demonstrated effective vaccination could be expected to net about $225 after the cost of the vaccine.
"As Dr. Pighetti pointed out at this year's NMC conference," Dr. Jones notes, "vaccination isn't the same as immunization. You have to correctly target the pathogen causing mastitis, and you have to allow the animal's system to correctly respond to that vaccination. The five S. aureas strains in Lysigen include one serotype 5, two serotype 8 and two serotype 336 isolates, the three predominant serotypes known to cause S. aureas mastitis. Targeted and managed correctly, vaccinating to help improve immunocompetence and boost the ability of the animal to mount an effective immune response against an invading pathogen is an important part of an effective mastitis control program, and a contributor to producing quality milk."
About Boehringer Ingelheim Vetmedica
Boehringer Ingelheim Vetmedica Inc., St. Joseph, Mo., is a subsidiary of Boehringer Ingelheim Corp., based in Ridgefield, Conn., and a member of the Boehringer Ingelheim group of companies.
The Boehringer Ingelheim group is one of the world's 20 leading pharmaceutical companies. Headquartered in Ingelheim, Germany, it operates globally with 135 affiliates in 47 countries and approximately 39,800 employees. Since it was founded in 1885, the family-owned company has been committed to researching, developing, manufacturing and marketing novel products of high therapeutic value for human and veterinary medicine.
In 2007, Boehringer Ingelheim posted net sales of US $15.0 billion (10.9 billion euro) while spending approximately one-fifth of net sales in its largest business segment, prescription medicines, on research and development.
For more information, please visit www.bi-vetmedica.com.