What are the four major factors that determine the success or failure of chicken immunization?

I. Vaccine factors

1. Selection of vaccines: Products produced by biological products enterprises that have passed GMP acceptance and have a formal production license and approval number from the Ministry of Agriculture should be purchased. When purchasing, carefully inspect the vaccine vials. Any vial that is broken, has no label, has unclear label printing, has a loose cap, contains impurities, has changed color, shows separation of the emulsion layer in inactivated vaccines, is expired and ineffective, or has not been stored under the prescribed conditions must not be selected.

2. Storage of vaccines: Store strictly according to the requirements of the instructions, avoiding repeated freezing and thawing caused by fluctuating temperatures, which can inactivate the vaccine or reduce its potency; direct sunlight is strictly prohibited; vaccines that have been diluted and are not used up, as well as vaccine vials and instruments, must be inactivated.

3. Time limits for vaccine use: Inactivated vaccines should be used up within 6-8 hours; live vaccines should be used up within 2-4 hours after dilution.

4. Precautions for vaccine use: Use strictly according to the requirements of the instructions, ensuring the appropriate dose and correct method; disinfection drugs, antibacterial and antiviral drugs, interferon and immunosuppressants, etc. are prohibited 7 days before and after vaccine use; adding an appropriate amount of immune boosters such as VA, VC and VE to the feed can improve the immune effect; before using a new type of vaccine, it should be trial-tested on a small scale, and only used on a large scale after no abnormal reactions occur.

In addition, vaccination instruments must be strictly disinfected to ensure one needle and one wing-web stab needle per chicken (at least per single cage), so as to avoid cross-infection.

II. Immunization methods

1. Intranasal and intraocular administration: Instill the diluted vaccine drop by drop into the eye or nasal cavity of each chicken.

2. Spray use: Spray with an aerosol spray gun 1 m above the flock. This method requires double the vaccine dose, requires special equipment, and also requires good airtightness of the chicken house.

3. Drinking water: Suitable for larger chicken farms. Water must be withheld in advance. Withhold water for 2-3 hours in summer and 3-4 hours in winter, so as to ensure that each chicken drinks enough vaccine in a short time. 0.1% skim milk powder or vaccine protectant (available on the market) can be added to the water to prevent the vaccine from being damaged by water.

4. Injection methods: Including subcutaneous injection, wing-web stabbing, and intramuscular injection.

III. Factors to consider in immunization timing

1. Local disease prevalence: If fowl pox has never occurred locally, and the sanitation and epidemic prevention work on the chicken farm is well done, fowl pox vaccine may be omitted; if Newcastle disease occurs frequently, Newcastle disease vaccine should be administered as early as possible.

2. Maternal antibody levels: If the maternal antibody level of chicks is high and vaccination is given too early, the effect of the vaccine will be reduced. In addition, the immune system of chicks is not fully developed, and the response to too-early vaccination is poor, so it cannot produce the due effect.

3. Antibody levels in the body: If the antibodies produced by the previous vaccination have not declined to a certain level at the time of vaccination, the effect of this vaccination will be weakened. Chicken farms with the conditions should preferably conduct antibody monitoring to determine the timing of vaccination.

4. Vaccine characteristics: For example, Newcastle disease strain I vaccine has strong side effects, and its use during the laying period will affect egg production. During this period, strain II or strain IV can be selected.

IV. Formulation of immunization programs

1. Grasp the prevalence situation: Before formulating an immunization program, the disease history of the chicken farm and surrounding chicken farms should be investigated, so as to determine the types of vaccines to be administered and the vaccination timing.

2. Primary immunization and booster immunization: Detect the maternal antibody level of chicks to determine the time of primary immunization; according to the time of antibody production, immune period or antibody detection results after vaccination with different vaccines, determine when to carry out booster immunization.

3. Infectious diseases: During an epidemic, for highly virulent infectious diseases or currently prevalent infectious diseases, inactivated vaccines and live vaccines can be used at the same time; it is best to select a vaccine consistent with the prevalent virus strain.

4. Age in days and susceptibility: For example, chicks are most susceptible to Marek's disease within 24 hours after hatching, so vaccination should be carried out within 24 hours after hatching.

5. Vaccination is not suitable under stress conditions.