Increasing the dose of the vaccine in broiler chickens and is it beneficial for the bird or not?

الدكتور ميلاد ابراهيم عريبي
10-20-2024

This question is important and is raised on a number of occasions. To answer it, we must know whether the increase is for the killed serum strain or the live serum strain? What is the method of giving the vaccine to the bird? What is the type of serum strain to be given at a double or even more than double concentration? We must also know the amount of (EID 50) or (TCID50) as well as its actual concentration during vaccine manufacturing, and know whether vaccine companies are reliable in manufacturing or not?

As for killed vaccines, in general and without exception, it does not matter what type of serological strain is present in the vaccine and the amount of virus present in the single dose for each bird, as we can give the double dose twice, three times or four times for each bird, without causing any inhibition or damage to the immune system. However, on condition that the injected amount is compatible with the size and location of the part in which this substance is injected. For example, four milliliters of vaccine cannot be given to a one-day-old chick, because the injection area will not be sufficient for this size of vaccine. As for killed vaccines, when given, whether at the recommended dose or more, and in specific places, especially in the subcutaneous area, the formation of the immune response depends on the first and second signals (signals 1 and 2), but there is a difference in this process if the dose is more than the prescribed or recommended. When giving a higher dose, immune stress will occur, especially in the injection area, and thus giving more than one signal to the DC or LC cells in the area to be fully prepared, due to the presence of a foreign body that has penetrated the important and highly resistant defensive barrier, which is the skin.

At the first and second signals, they will activate the T cells, due to the presentation of antigens (Ag) by the (APC), which the (DC) will crush, destroy and fragment the antigen (Ag) and convert it into small parts, so each antigen (Ag) will display its complete parts with complete information on the surface of these cells, which the (T) cells will bind to and form what is known as (polyclonal antibodies) for each antigen (Ag) that it has taken.

The first signal (signal 1) occurs through the connection of (CD4 and CD8) and the T cells receptor known as (TCR).
The second signal (signal 2) occurs when CD28 and B7 are connected and interact. These two signals are what will activate the cells and release cytokines and interleukins strongly. The more the killed antigen inside the vaccine, the stronger the cells will bind to it and the more the T cells will be activated and transformed from naive cells into advanced and active cells. These two signals are responsible for releasing and stimulating IL 2, which is responsible for the beginning of the immune response and the beginning of the third signal (signal. 3). Scientists and researchers have recently confirmed that T cells need dual signals for activation and differentiation. It has been shown that giving a killed and inactive antigen (Ag) can greatly stimulate and differentiate these cells depending on a group of cytokines formed as a result of the high threat that the immune system evokes when the antigen (Ag) enters in a larger number than the scheduled one, which in turn has confused the immune system and caused it to be under pressure due to the entry of the antigen (Ag) from a strong and important line of defense such as the skin. Researchers discovered that after activating, differentiating and completing the immune signals after that, and when giving a large amount of antigen (Ag), especially the killed ones, differentiation and activation of other sub-cells (T) will occur, not like the differentiation and activation of the first (T) cells, as the new cells will take on a new differentiation in the speed of the immune response, which in turn will shorten the first process in forming the antigen (Ab), so (B cell) cells will turn into (plasma cell) faster and more, and thus the formation of immune bodies will be more standard (titter) and can be detected by the ELISA or HI device. For more than three years, we have been giving killed vaccines in doses higher than the doses recommended by the manufacturer, and I have examined the titers myself by the ELISA device and also by the (HI) and the results were very good. These results provided the necessary protection when the same serum strain of the bird entered and was similar to the killed serum strain and the vaccine with which the bird was vaccinated.

The process of giving a dose greater than the actual dose in killed vaccines, and in all honesty, was among the recommendations of my professor Dr. Fouad Al-Sheikhly.

As for live vaccines, I have a special and multiple opinion due to the large number of live viruses given to poultry, as the (ND) virus differs in administration from the Gumboro virus and differs from the IB bronchitis virus.

التوصيات:
Giving killed vaccines subcutaneously in poultry farming in double or triple doses increases the process of forming antibodies within the same time specified in the immune response process, and thus will increase the level of immunity protection against the same serum strain that infects the hall and is similar to the killed serum strain in the oil vaccine.