Cows that have a compromised or poorly functioning immune system are more prone to illness in early lactation than at any other time in the production cycle, with immunity dipping by up to 40% during the transition period.
The cost of these issues can be staggering, with a 100-cow herd likely to see annual costs in excess of £11,000 in dealing with mastitis, metritis and retained placentas as a direct result of immune system suppression.
In the current challenging dairy climate, these are costs few farms can afford to carry.
What is cow immunity and why is it challenged at this stage of production?
Immunity is essentially a cow’s ability to fend off infections and disease challenges. Cows have a broad non-specific “innate” immunity, which can be enhanced with the help of an “acquired” immune response.
This develops after previous exposure to disease or following a proactive vaccination programme.
The challenge to immunity around the transition period is an entirely natural and common phenomenon, with a cow’s neutrophil (white blood cell) and lymphocyte (element of the blood specifically linked to the immune system) function decreasing by 25-40%.
This greatly increases the risk of milk fever, retained cleansings, metritis, LDAs, ketosis and mastitis – all of which are commonly seen in early lactation.
A cow’s immune system doesn’t function as well as it should because the cow has to undergo changes to its physiology and immune function to accommodate the developing placenta and foetus.
As a result, transition cows are both more likely to become infected by pathogenic organisms and to suffer more severe disease than at any other stage in the production cycle.
Allied to this natural immune suppression is the effect of negative energy balance in the pre- and post-calving period and the difficulty of getting nutrition and management spot on in this tricky stage.
Steps to improving cow immunity
The reasons for immune suppression in this period are complex and still poorly understood and undoubtedly we will learn more about it in the coming years – but what can farmers do in the meantime?
1 Transition cow health issues rarely occur in isolation and higher risks of one problem will increase the chances of something else developing too.
For example, cows with milk fever are more likely to develop retained cleansings, metritis, endometritis and mastitis, and those with negative energy balance are also at higher risk of left displaced abomasums, retained cleansings, metritis and endometritis.
These common problems are often different ways of the cow trying to tell you the same thing – her immunity is compromised.
It is, therefore, vital that, as farmers and vets, we do all we can to support the immune system function around calving. Boosting the immune system at calving through good nutrition and management has long been a core part of transition cow management.
2 Improving energy balance and preventing ketosis are also central to maximising immune function at calving.
Recent studies have proved that cows suffering one of the common post-calving problems were likely to have had poor energy status before calving. This means she was already a high-risk cow before she even calved.
3 Use your disease recording with your vet and nutritionist to help you identify whether or not your cows’ immune status is being compromised by transition health.
The benefits of improving immunity
Improving the immune system will result in fewer cases of severe infections requiring antibiotic therapy and a quicker return to positive energy balance and increased fertility.
This will allow cows to return to service quicker, a key part of profitable dairy farming.
Importantly, while transition nutrition management is a key part of helping cows maintain a healthy immune system, it is also central to maximising milk production early in lactation.
There are no simple answers to overcoming immune suppression at calving.
It is a challenge every cow faces and one that is best countered with careful planning, monitoring of performance and teamwork from vet, nutritionist and farmer.