Despite being one of the most important phenotypes in agriculture, the immune response is a trait we know the least about.
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The rationale for immune phenotypes:
- Ask any farmer what his cows average milk yield is and he can tell you immediately - Ask any livestock producer what his meat yield score on a carcass is and he can tell you that too. But ask anyone what their herds immune status is, and you wont get a definitive answer. That's because we don't routinely measure the immune system, despite the fact that optimal immunity underpins the successful capture of all production and longevity traits. Our mission is to make measurement of immunity routine on farm. With our know how, we can compare between cows, between farms, between production periods and even across countries. With this valuable insight, we can then identify animals with a poor immune response, those that do not benefit from vaccination and also those that are likely to act as a reservoir of infection. Furthermore, once we know what our baseline is, we can then evaluate the effects of national selection policies on immune competence over time. |
Measures of immunity:
The most common measures of the immune response that people would be familiar with are 1. Immunoglobulins in colostrum and 2. Antibody responses to vaccination. But even with these we don't assess them routinely. In addition, the immune response is complex and these two measures don't tell the whole story. Both immunoglobulins and antibody responses measure the activity of one one cell type - the B cell. Immunoglobulins are made by maternal B cells and passed to the calf in milk. the calf can make its own antibodies after a vaccination when its immune system is mature enough (and when the vaccine antigen is not targeted by the immunoglobulins!).
So those two markers are of only one cell type, and cows have many different cell types. So measuring immunity needs to measure at least the predominant cell types in order to accurately measure the immune response.
The problem with clinical disease:
The appearance of disease symptoms is often the first sign that a farmer or vet recognises that disease is present. However clinical signs appear at a relatively late stage in the disease process and infection can be well established. This leads to animal welfare issues, poor responses to treatment, additional costs and often requires more treatments (including antibiotics). A lot of processes happen prior to the onset of clinical disease and therefore accurate and sensitive measures of immunity (often called biomarkers) could flag these issues before an animal gets infection, or during the early (sub-clinical) stages of infection.
Immunosuppression:
Many healthy individuals can resist infection without developing disease. So the presence of a pathogen (e.g. E. coli) doesn't necessarily lead to disease. Here again, routine immune measures would enable us to identify an animal whose immune system is depressed (say due to nutritional deficits) or compromised due to additional infections that make it disease susceptible. Measures of immunity will ultimately enable farmers and vets to move form reactive medicine to proactive herd health management.
Disease-Resistant cattle:
There is a difference between Disease Resistant and Disease Resistance! Resistance is usually* multifactorial and therefore a dynamic entity that varies according to pathogen factors (including level of infection) as well as host factors (like immunosuppression and/or secondary infection).
*some cases of individuals missing cellular receptors which mediate viral (e.g. HIV) entry are documented, and therefore these individuals are truely resistant. However, that is not usually what we refer to when discussing disease resistance across a population of animals.
The most common measures of the immune response that people would be familiar with are 1. Immunoglobulins in colostrum and 2. Antibody responses to vaccination. But even with these we don't assess them routinely. In addition, the immune response is complex and these two measures don't tell the whole story. Both immunoglobulins and antibody responses measure the activity of one one cell type - the B cell. Immunoglobulins are made by maternal B cells and passed to the calf in milk. the calf can make its own antibodies after a vaccination when its immune system is mature enough (and when the vaccine antigen is not targeted by the immunoglobulins!).
So those two markers are of only one cell type, and cows have many different cell types. So measuring immunity needs to measure at least the predominant cell types in order to accurately measure the immune response.
The problem with clinical disease:
The appearance of disease symptoms is often the first sign that a farmer or vet recognises that disease is present. However clinical signs appear at a relatively late stage in the disease process and infection can be well established. This leads to animal welfare issues, poor responses to treatment, additional costs and often requires more treatments (including antibiotics). A lot of processes happen prior to the onset of clinical disease and therefore accurate and sensitive measures of immunity (often called biomarkers) could flag these issues before an animal gets infection, or during the early (sub-clinical) stages of infection.
Immunosuppression:
Many healthy individuals can resist infection without developing disease. So the presence of a pathogen (e.g. E. coli) doesn't necessarily lead to disease. Here again, routine immune measures would enable us to identify an animal whose immune system is depressed (say due to nutritional deficits) or compromised due to additional infections that make it disease susceptible. Measures of immunity will ultimately enable farmers and vets to move form reactive medicine to proactive herd health management.
Disease-Resistant cattle:
There is a difference between Disease Resistant and Disease Resistance! Resistance is usually* multifactorial and therefore a dynamic entity that varies according to pathogen factors (including level of infection) as well as host factors (like immunosuppression and/or secondary infection).
*some cases of individuals missing cellular receptors which mediate viral (e.g. HIV) entry are documented, and therefore these individuals are truely resistant. However, that is not usually what we refer to when discussing disease resistance across a population of animals.