The immune system of a cow is comprised of a large network of specialised cells, embedded in all organs and tissues throughout the cow’s entire anatomy. There are two types of immune functions: the innate immune function and the adaptive immune function. In this blog, we will elaborate on both of them.
The innate immune function provides initial protection in reaction to pathogens. This immune function is fast and unspecific, which means that it works in the same way regardless of the type of pathogen it has to combat. Examples of this innate function are physical barriers in the body of the cow, such as the skin and nasal secretions. Another way in which the innate immune function works is through cells that recognise pathogens and start getting rid of them. These cells include macrophages and neutrophils. Macrophages are embedded in all body tissues and act as sentinel cells: as soon as they detect a pathogen, they release alarm signals that call neutrophils for help. Neutrophils are first responders when help is requested by macrophages. Normally they circulate in the blood, from which they migrate to the areas where they are called to action. Their function is to destroy pathogens, mostly by engulfing them (a process called phagocytosis).
Lymphocytes are key cells that assume actions that take longer time to develop but are more specific against each pathogen and include the production of immunoglobulins or antibodies. The antibodies help with signaling and neutralising the pathogens. Adaptive immunity, unlike the innate type, has memory. This means that the next time the cow encounters the same type of pathogen it will respond much quicker with the production of specific antibodies and other specialized functions.
Neutrophils travel in the bloodstream in numbers of several million per millilitre in healthy cows. To reach their work site, they must leave the blood vessels and penetrate the underlying tissue where an infection is developing. The migration of the neutrophils from the blood vessels to the tissue is highly regulated by a series of receptors and chemical factors. Key components that are required to make this process work are present on the surface of healthy neutrophils, for example L-selectin (a protein that binds the neutrophils to the blood vessel walls that they will eventually cross), and certain receptors for interleukins (chemical factors released by other cells that among other functions will direct the neutrophils to the infected area). L-selectin and interleukin receptors have been used as markers of neutrophil function. These markers can be measured in neutrophils isolated from live animals, and they tell us about the functionality of that animal’s immune system. Certain functions of neutrophils such as phagocytosis can be directly measured in vitro. These are some examples of different approaches that can be used to objectively estimate the immune competency of a cow.
As with any other body function, immunity is subject to ups and downs. Immune competency varies across cows because of genetics, age, and intrinsic variability. But it also varies day-to-day within the same animal. Stress is a key factor that creates drops in the immune competency of cows. The cow responds to stress by releasing cortisol, which induces several metabolic adaptations to respond to the challenge. However, cortisol has a negative impact on the immune system: among other effects, cortisol affects neutrophil function by decreasing L-selectin on the surface of neutrophils. One of the effects of the impaired immune function is decreased reproductive performance. Read more about this in this blog article.
OmniGen is a scientifically proven product that helps to support healthy immune function, even during stress events. A healthier immune function may result in higher production and less health events. Contact us to learn more about how OmniGen can optimise your farm.