Detailed Explanation of Disease Prevention and Control Strategies for 4- to 6-Week-Old Chickens

1. Lock down and isolate the brooding area to prevent disease transmission via personnel, supplies, vehicles, other chicken flocks, and other routes. Maintain hygiene inside and outside the chicken house; persist with disinfecting the chickens in place and disinfecting the environment outside the house. When no live vaccine immunization is being carried out, ensure disinfection twice a day to reduce the pathogen load in the environment.

2. At this stage, the flock transitions from having a preliminary ability to regulate body temperature to being fully able to regulate body temperature. Therefore, in the relationship between temperature and ventilation, it should gradually shift from prioritizing warmth during 0 to 3 weeks to placing equal emphasis on temperature and ventilation, and finally to prioritizing ventilation. In the later period, when ventilation and warmth conflict, first ensure ventilation and air exchange in the chicken house, and then consider temperature. In light control, reduce light intensity to below 10 lux.

3. Continue to supply the flock with highly nutritious, complete, and balanced feed.

4. The immune organs of the chicks are basically mature and can produce a good immune response, so immunization against avian influenza, infectious laryngotracheitis, and fowl pox should be strengthened.

5. Carefully observe the flock at least once a day for mental state, feed intake, water intake, feces, respiratory symptoms, and so on. When there are signs of disease occurrence, promptly determine the disease type and take measures to control further development of the disease.

At this stage, focus on preventing and controlling the occurrence of Newcastle disease and fowl pox, while also doing a good job of immunization against infectious laryngotracheitis.

1. Newcastle disease

Because the immune system of chicks is not fully developed, no matter what immunization program is used, it is difficult to ensure the production of good humoral antibodies. Therefore, during the chick stage, good protection for the flock mainly relies on local mucosal antibodies produced by live vaccine immunization. In the current domestic environment, chicks face the threat of Newcastle disease virus at any time after hatching. Considering that the production of local mucosal antibodies is minimally affected by maternal antibodies, Newcastle disease live vaccine should be administered promptly to produce local mucosal resistance against disease infection as early as possible. It is best to do this at 1 day of age, and no later than 3 days of age.

The combined use of live vaccines and inactivated vaccines can achieve complementary advantages and produce strong protection against disease. Oil-emulsion inactivated vaccines, after adding oil adjuvant, have significantly enhanced immunogenicity, are less interfered with by maternal antibodies, and can induce the body to produce strong and lasting immunity. Immunization during the chick stage must protect the entire brooding and rearing area, and the antibodies produced by immunization before laying need to protect the entire laying cycle. Therefore, immunization at these two stages should combine live vaccines and inactivated vaccines.

The occurrence of Newcastle disease in chickens is mainly atypical, because flock antibody levels are uneven. Therefore, monitoring flock antibody levels is very important. Ensure HI antibody levels are no lower than 6 during the rearing period and no lower than 9 during the laying period, and also ensure immunization with an attenuated vaccine once every 2 to 3 months during the laying period.

After Newcastle disease occurs, emergency immunization with a high dose of attenuated vaccine can be used, supplemented by antibiotic treatment to prevent secondary bacterial infection.

2. Infectious laryngotracheitis

2.1 Strictly isolate affected chicken houses from unaffected chicken houses, disinfect thoroughly, and strengthen feeding management to prevent spread.

2.2 Immunization: first immunization at 5 to 6 weeks of age, second immunization at 13 to 14 weeks, which can protect the entire laying period; when immunizing, carefully select vaccine manufacturers, strictly control vaccine dosage, and choose vaccines with good immunization effects and few side effects, with the immunization dose not exceeding 1 dose; to prevent immune reactions, administer drugs sensitive to the respiratory tract during immunization to control the occurrence of conjunctivitis; use eye-drop immunization, preferably immunizing one side, to prevent conjunctivitis from appearing in both eyes at the same time; there is interference with immunization using Newcastle disease live vaccine, so the two immunizations should be spaced more than 10 days apart.

2.3 Emergency vaccination. This disease spreads slowly. For flocks diagnosed early, emergency vaccination with vaccine can achieve good results.

3. Fowl pox

For this disease, using vaccine wing-web stab vaccination twice can control the disease well. Generally, the first immunization is at 2 to 3 weeks of age, and the second vaccination is carried out at 4 to 5 months of age. During wing-web stab vaccination, use a standard specialized stab vaccinator, and at the same time check whether the needle groove is full of vaccine liquid; it is strictly forbidden to stab into muscle or bone; 7 to 10 days after stab vaccination, check the immunization effect; because the local immunity appearing at the vaccination site can be maintained for a long time, performing a second vaccination at the same site will result in a poor immunization effect. Therefore, the second vaccination is preferably performed on the side opposite the first vaccination site; due to the biological characteristics of this virus (epitheliotropic virus), stab vaccination is the most effective immunization method.