Chickens and turkeys are most often grown on intensive farms where the number of birds per square foot is maximized so that the most efficient – and profitable – poultry production can be undertaken. Unfortunately, with high densities and frequent turnover of flocks, the opportunity for disease-causing organisms to take hold of your flock is ever present. Some diseases cause minor delays in growth rate when stress may reduce appetite; other diseases can cause mortality from 25% up to 100% of your flock if untreated. (see our article on the vaccines we currently administer to our chicks).
Viral infections are one of the types of diseases that have a major impact on poultry around the world, with some of those viruses being treatable by vaccinating the birds to prevent infection in the first place. Highly Pathogenic Avian Influenza is one of the viral diseases that is in the headlines at the moment, causing high economic loss around the world. Modern Scientific research has also suggested that a chicken’s immune system may not fully develop until approximately 4 weeks of age, requiring broiler farmers to provide supplemental protection against the major disease threats.
Commercial Breeder Farm Vaccinations
The first line of defense is “Maternal Antibodies.” Commercial fertile hatching eggs used in Barbados are imported from breeder farms in the USA, Canada and Europe. All follow strict vaccination programs with their breeders. Vaccination causes the hen to have an immune response, building up anti-bodies that fight the target virus of the vaccine. When that hen lays an egg, she shares her antibodies (immunity) with that egg. The chick that hatches from this egg will have a degree of ‘instant immunity’ at one day old from the challenges that its mother has been exposed to.
Breeder flock vaccination is an extremely important, and complex, part of producing high quality hatching eggs. One of our suppliers, for example, shares the following as their broiler breeder vaccination program leading up to the flock producing eggs for sale to hatcheries:
As the chick grows, however, the effectiveness of maternal antibodies decreases – vaccination at one day old in the hatchery now becomes important.
Hatchery Vaccination
Vaccination in the hatchery at a day old creates an immune response, which in turn builds up antibodies against the target virus. The response is not immediate, it can take up to 14 days for the full level of antibodies to be formed. As the maternal antibody protection drops, the day-old vaccination protection builds up, preventing periods of little to no immunity. Layers and turkeys sometimes require booster vaccines by virtue of the time they will be alive, and their immune system losing its effective response over time.
Commercial hatcheries employ three major methods of vaccinating chicks;
In-Ovo vaccination requires very sophisticated equipment to vaccinate full incubator trays of eggs at 18 days old, 3 days before hatch, while they are being transferred from incubator to hatcher. A small hole is pierced into the egg shell around the air-sac, vaccines are injected into the unhatched egg, and are absorbed by the almost fully developed chick. No manual vaccination is required. This method requires large investments in equipment and is generally only utilized by hatcheries producing half a million chicks per week or more.
Subcutaneous injection, or ‘below the skin’ injection, is the method used by hatcheries in Barbados. Day old chicks are vaccinated individually using a device that allows the handler to pick up a chick, press it against a sensor, a rapid injection occurs, the chick is counted and placed in a box. When the box count is reached, an audible alarm signals the need to start on a new box. One well trained handler can vaccinate 15,000 chicks in one day in ideal conditions.
Spray booth vaccination is as it sounds – some vaccines cannot be mixed together during subcutaneous injection, or are more effective when absorbed through the eyes or by breathing them in. Boxes of chicks are passed through a spray booth that creates a fine mist which attaches to the tissues in the eyes and the respiratory tract, or forms droplets on each chick that other chicks instinctively eat.
Gale’s Agro Products utilises subcutaneous injection of varied vaccines depending on the type of bird being produced. Broiler chicks receive one vaccination against Marek’s Disease, Infectious Bursal Disease and Newcastle Disease. Layers also receive Fowl Pox vaccination, while turkeys receive ONLY Fowl Pox at the hatchery. Fowl Pox should be repeated as a booster on the farm for both layers and turkeys at the appropriate age – often in combination with a cholera vaccine. We have selected these vaccination strategies to protect against a few of the most devastating poultry diseases, however it is important to understand that one vaccine doesn’t protect against ALL diseases; there are many, many poultry disease causing viruses and bacteria some of which can be vaccinated against, and others that require strong biosecurity programs to avoid allowing then into your poultry house. One application of vaccine also does not guarantee a life time of bird immunity in most cases – Fowl Pox, for example, has to be administered again at 8 to 12 weeks in order to ‘boost’ the chicken’s immune response and carry that fowl pox virus immunity through to adulthood.
