The capacity to fend off illness is known as immunity (also called resistance).
Domestic chickens frequently require assistance to build immunity against diseases in their surroundings since they are kept in an unnatural habitat.
Inherited Immunity
Inherited immunity is a type of immunology that involves the transfer of immunity from hen to chick. It is a natural defense mechanism against pathogens and other foreign organisms that can cause disease in chickens.
A chick is born with some degree of innate/hereditary immunity. As it matures, it picks up additional immunities.
Inherited immunity protects chicks from diseases until their own immune system has had time to develop its own protection against infection.
Complete Immunity
Immunity is considered complete when it extends to the entire chicken species.
Chickens have complete immunity to a broad range of diseases that infect other animals and birds but never affect chickens.
Chickens are also immune to various diseases that they frequently carry in their bodies. However, if their immunity is compromised they become ill.
Partial Immunity
Partial immunity occurs when only a few breeds, strains, or Individual chickens are resistant to a particular disease.
For example, because some chicken breeds never die from Marek’s illness, chickens are said to have partial immunity.
Acquired Immunity
Acquired immunity is a type of protection given to a chicken after an infection or by receiving a vaccine. It involves developing antibodies against a particular virus or bacteria in order to protect the body from future infections.
Passive Immunity
Antibodies made by a source other than the chicken’s own immune system is known as passive immunity.
Chickens can either develop passive immunity naturally or artificially:
Natural Passive Immunity: A chick inherits natural passive immunity from a hen through the egg. The cause of maternal antibodies could be a sickness or vaccination the hen previously had.
Artificial Passive Immunity: When a chicken receives an injection of an antiserum containing antibodies to combat a particular pathogen or an antitoxin to combat toxins produced by bacteria, it develops artificial passive immunity.
Active Immunity
There are 3 key ways in which active immunity differs from passive immunity:
- The immunity is brought on by antibodies made in a chicken’s own body.
- The development of the immunity takes time, typically weeks.
- In comparison to passive immunity, active immunity lasts longer.
Although active immunity always outlasts passive immunity, it can be either temporary or permanent if stress doesn’t compromise the chicken’s immunity to infection.
Active immunity against bacteria is typically temporary and reliant on stress avoidance, whereas active immunity against viruses is usually long-lasting.
Similar to passive immunity, active immunity can be developed through natural or synthetic means:
Natural Active Immunity: When a chicken’s body generates antibodies to combat a specific disease, this is known as natural active immunity. Also, during incubation or at any time after hatching, a chicken can potentially develop active immunity.
Artificial Active Immunity: A vaccine containing antigens that prompt a chicken’s body to develop antibodies against those specific diseases offers artificial active immunity. Occasionally, vaccinations need to be renewed with one or more booster shots.
Chicks & Immunity
According to a commonly repeated suggestion, growing chicks should be raised separately from mature hens to maintain their health.
But how do chicks raised by hens ever survive?
The answer is that the chicks inherit maternal antibodies. Then, over time, chicks go on to gain more immunities through a process called trickle infection that results from exposure to the pathogens in their surroundings.
Brooder-reared chicks do not benefit in the same way. Instead, they are kept apart from other chickens in an unnatural setting. If they are later placed in a mature flock, the chicks’ immune systems might be overworked by exposure to too many diseases at once, causing to illness.
So, giving brooded chicks some soil to scratch in while they are still in the brooder is an easy way to expose them to the pathogens they will likely come into contact with later in life.
The sooner chickens have the chance to scratch and peck on dirt, the quicker they will build an immunity to the viruses that will be present in their future surroundings.