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Improving vaccinal response with Original XPC


Jonathan Broomhead, Ph.D., Manager, Global Poultry Research and Technical Support, Diamond V

Vaccination is an important step in protecting animals from disease agents such as viruses, parasites, and pathogenic bacteria. The success of a vaccine program relies on several factors, including the timing and efficacy of the vaccine.


Serological testing is one of the most common methods to evaluate vaccine antibody response or vaccination efficacy. Length of time following vaccination is important for determining efficacy of the vaccination, as one to four weeks may be necessary to reach protective levels of antibodies depending on the test used and the disease involved.


Hemagglutination inhibition (HI) is the most widely used serologic test used for measuring protection (detecting antibodies) from several vaccines such as Mycoplasma gallisepticum, M. synoviae, infectious bronchitis, and Newcastle disease.


The methodology of the HI test is serially diluting blood serum and mixing with red blood cells (RBC; from Specific Pathogen Free or unvaccinated birds, free from the vaccine antibodies) and the appropriate antigen. The HI titer score is determined, at the point (highest dilution level) in which the agglutination of RBC's is no longer inhibited.


HI titer results are often reported as log base 2 (because of doubling dilution sequence) with a Geometric Mean Titer (G.M.T.) calculated for the flock. With a more intensive initial testing program (increased number of birds tested and several flocks tested) a 'normal' baseline curve can be established and can be used for subsequent flock/vaccine monitoring. The results of these tests can be subjective and vary from lab to lab, so the same lab should be used for continuous monitoring of flocks.


Birds that are immunosuppressed prior to vaccination due to underlying factors such as environmental stress, virus exposure, mycotoxin consumption, etc. will be less responsive to a vaccine. These stressed birds will have an adaptive immune system that is not functioning properly. Birds should not be vaccinated when under stress, and instead, waiting until they are healthy before vaccination.


In contrast, young and newly hatched chicks from breeder hens that have high antibodies to a specific disease will have higher maternally transferred antibodies. Vaccinating chicks with the same vaccine, when maternal antibodies are still present, will limit the ability of the chick to develop its own antibody response. The maternal antibodies may inactivate the vaccine virus, decreasing its response.

Other than potential vaccination application issues, administering a vaccine that has low activity (due to improper production or storage) will result in reduce vaccine antibody titers and efficacy against disease.


The activity of a vaccine is measured and reported as 50% infectivity (EID50; amount of virus that will infect 50% of inoculated eggs) and Hemagglutinating activity (HA). Researchers (Abbas et al, 2006) tested 5 commercial Newcastle disease vaccines for activity and subsequent antibody titers and efficacy during a challenge.


Results of this research demonstrated correlation between vaccine activity (efficacy) and antibody titer and subsequent protection during a challenge.


Diamond V Original XPC™ has been shown to balance the immune system by supporting both innate immunity and adaptive immunity. A specific example of how Diamond V's fermentation metabolite products support adaptive immunity has been evaluated by measuring the antibody titer response in broilers given Newcastle disease vaccine (NDV).


In conclusion, feeding Diamond V fermentation metabolites increased NDV antibody titers in all four of the broiler studies, indicating that Original XPC affects adaptive immune function. The increased antibody levels in broilers fed Original XPC may improve disease protection following vaccination.



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Article made possible through the contribution of Dr Jonathan Broomhead and Diamond V.

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