Proper use of bacterins in broiler breeder operations

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This article is a practical guide to induce optimal levels of immunity and minimize the risk of adverse effects associated with the use of bacterins in broiler breeders.

A good vaccination program, combined with appropriate management and good biosecurity, plays a key role in promoting the health, well-being and productivity of broiler breeders.

Inactivated bacterins or bacterial vaccines can be a valuable tool in breeding programs, to stimulate high levels of immunity against pathogens such as:

• Salmonella spp.
• Pasteurella multocida (cholera)
• Escherichia coli (E. coli)
• Avibacterium paragallinarum (coryza)
• Ornithobacterium rhinotracheale (ORT)

• Bacterins should be used under the supervision of specialized veterinary doctors.
• It is important to use products of reliable manufacture. Their storage and handling must be adequate.
• Bacterins must be at the correct temperature before administration.
• These products require handling and application by trained personnel.
• The vaccination process must be under constant audit.
• Visual inspection of the injection site and technique is the best method of evaluating your administration.
• It is essential to vaccinate all birds.
• An unvaccinated bird will not be able to develop the desired immunity to these inactivated products.
• The goal is to induce long-lasting high antibody levels.

• Bacterins consist of two components, a liquid phase and an adjuvant mixed together to form an emulsion. The liquid phase contains the antigen or antigens of specific bacteria and the adjuvant is a substance that helps to strengthen and prolong the immune response of the bird.
• The antigen can be part of the bacteria or components of it.
• In the case of the adjuvant, aluminum hydroxide and mineral oil are the most commonly used. Simple emulsions consist of a liquid phase surrounded by a continuous oil phase, referred to as a water-in-oil (H₂O/Oil) emulsion.
• Dual emulsions (H₂O/Oil/ H₂O) are made by dispersing water in oil and then dispersing this H₂O/Oil emulsion in water in order to make them less dense and to facilitate their injection.
• The reaction at the injection site of oil-emulsion bacterins is more severe than the reaction caused by inactivated viral vaccines. This is due to certain potentially toxic bacterial components, such as lipopolysaccharides or endotoxins.
• The reaction to bacterins in oil emulsions tends to be more severe and produce higher levels of antibodies compared to emulsions in aluminum hydroxide.

Due to the potential of bacterins to cause a strong reaction, they are generally administered between 8 and 10 weeks of age when broiler breeders have enough weight and muscle mass to assimilate them. A second dose is recommended between 18 and 20 weeks so that the flocks can overcome the reaction without compromising their weight, uniformity, sexual development and start of egg production.

It is recommended to remove the bacterial from the refrigerator around 24 hours before administration to temper them. To avoid breaking the emulsion, it is very important not to freeze them or allow them to overheat. Overheating can result in the release of endotoxins that can cause very severe reactions and mortality (post-vaccination bleeding syndrome).

The success of the bacterins and the severity of the reaction depends on the following factors:

• Good planning and proper management prior to administration
• Proper application technique
• Administration of a full dose
• Do not overlook or leave birds unvaccinated
• Physical state (age, weight) and health of flocks to achieve good immunity with minimum adverse reactions
• Training of personnel involved and audits of management and administration methods
• Following the manufacturer’s recommendations

In general, when the bacterins are applied correctly through the subcutaneous route (SC), there is less reaction when compared to intramuscular injection (IM).

SC injections

It is essential to use new sterile needles and replace them periodically (at least once every 500 birds). For SC injections, it is recommended to use 18-19 gauge needles and 10 to 12 mm (0.4 to 0.5 in.) Long. For IM injections, 18-gauge and 0.25-inch long needles are recommended. Blunt neeedles or with damaged bevels should be replaced immediately so as not to cause damage to the birds’ tissues.

IM injections

When the IM route is used, the breast muscle is the best possible site as its thickness offers good injection cushioning. When injecting into the breast, make sure that the needle is located 2.5-3.8 cm (1-1.5 in.) Away from the sternum or keel bone (Figure 5) and place the needle in the upper third of the breast, downwards at a 45 ° angle, preventing the application of the vaccine within the abdominal cavity. The application of bacterins to the leg muscles is not common in broiler breeders and in general should be avoided to prevent adverse reactions. Visual inspection of the administration technique (at the time) and localization of the vaccine in the correct place is the best method to determine the precision of the injection.

Inspection of the location is recommended within one hour after vaccination. Wet feathers indicate that the vaccine was misapplied. To visually evaluate the procedure after intramuscular (IM) application, it is suggested to cull some birds that are sexing errors (using a suitable method) and inspect the injection site.

If the birds are depressed and lethargic for a few days due to the reaction, it is recommended to adjust the amount of feed to stimulate and give the flock an additional amount of energy. This helps maintain weight uniformity and helps birds to cope with both tissue and systemic reaction. The post-bacterial hemorrhagic syndrome that occurs in some cases is an adverse reaction that is possibly due to the presence of endotoxins in some bacterins. In these cases, it is common to find an inflammatory reaction at the injection site of the vaccine in the breast. To avoid or reduce the incidence of these problems, it is imperative to have good vaccination planning, management and administration of vaccines and adequate age of the birds (avoid the administration of bacterins separated by a few weeks). Likewise, it is recommended to avoid bacterins that cause very severe reactions.

Scars at the injection site followed by application to the breast can result in seizure problems when the birds are processed at the end of the production cycle. These scars tend to be more visible when oil emulsified bacterins are used compared to inactivated viral vaccines. In order to reduce adverse reactions, some manufacturers have available bacterins with smaller volumes (250 ml bottles, 0.25 ml per dose) with the same concentration of antigens as conventional products (500 ml bottles, 0.5 ml per dose). ).