The costly condition of bovine respiratory disease (BRD) can cause irreversible damage to a calves lungs, so producers should think about how to prevent it and know how to rapidly identify and treat it, says vet Tim Potter.
BRD, or pneumonia, is a cause of major economic loss for the cattle industry, with estimates for the annual cost of the disease running to more than £60 million.
Tim Potter, senior clinical director of Westpoint Farm Vets, says on an individual case level, the cost is estimated at about £43, with this figure including the costs of treatment and the immediate check in growth rates.
However, Mr Potter adds the long-term costs of the case can be far more significant.
He says: “Estimated overall costs are closer to £772/animal by the time you factor in the delay to first calving, reduction in first and second lactation milk yield and increased risk of culling.”
BRD is complex interaction between disease-causing viruses and bacteria and the animal’s immune system which can be influenced by external stress factors, explains Mr Potter.
He says: “The important viral causes of respiratory disease are bovine respiratory syncytial virus, parainfluenza-3 virus and IBR.”
He adds that bovine viral diarrhoea may also be associated with pneumonia in some herds due to the negative effects it has on an animal’s immune status.
These viruses, he reminds farmers, can cause disease by themselves or damage the defence mechanisms of the upper respiratory tract and predispose to secondary bacterial infections of the lungs.
“There are a large number of bacteria which can cause disease in their own right or act as a secondary invader following viral damage to lung defence mechanisms.
“The important bacteria associated with BRD are mannheimia haemolytica, pasteurella multocida, histophilus somni and mycoplasma bovis.”
An animal’s susceptibility to BRD will be influenced by the strength of its immune system. And Mr Potter says on young calves the single biggest factor affecting the immune system is colostrum.
Mr Potter says: “Ensuring calves receive adequate good quality colostrum as quickly as possible after birth will give them the best possible start in life and help reduce the risk of disease.
“A calf’s immunity will also be affected by nutrition, management practices, stress and the environment, with issues in any of these areas having a negative impact on the calf’s ability to fight disease.”
When faced with an outbreak of BRD, the priority is treatment of the affected animals and minimising the spread of disease within the group.
Mr Potter says: “Treatment will be most effective if it is given as early as possible in the course of a disease, so it is important animals with BRD are rapidly identified and treated correctly.
“You should look out for coughing, nasal discharge and laboured breathing. If you are concerned about an animal, taking its temperature can help identify animals with disease. A temperature above 39.5degC indicates there is an infection.
“Treatment success is determined in part by how rapidly it is administered so ensure you have agreed treatment protocols in place with your vet and that all of your team know what they are and when to use them.”
Because of the bacterial component of the disease, antibiotics remain the mainstay of pneumonia treatment, but Mr Potter adds it is essential they are used correctly and following the principals of responsible use.
“Your vet will be able to advise exactly which product to use along with doses and it is essential you follow these instructions.
“Antibiotics used to treat pneumonia will ideally have a targeted action on the lungs, where the bacteria will be found along with a good length of activity to ensure the calf will be covered against any potential re-infection while it recovers and also minimise the need for additional handling.
“Because much of the damage to the lungs is caused by the calves inflammatory reaction to the pathogens, non-steroidal anti-inflammatory drugs are often employed in the management of BRD to reduce rectal temperature, increase appetite and decrease lung damage.”
While maximising treatment efficacy, it is important the goal should always be disease prevention, says Mr Potter.
“BRD is a multifactorial disease complex and it is important to consider all the potential risk factors when looking at control programmes.
“Changing the environment while not addressing underlying issues with colostrum management is unlikely to bring about significant improvement in performance. “Similarly, you are not going to get the best out of any vaccination programme if you do not address issues with poor ventilation or overstocking.”
In the housed environment, a constant supply of fresh air is essential in preventing BRD.
Mr Potter explains good ventilation removes stale, humid air which helps ensure viruses and bacteria cannot survive for long outside the animal.
He says: “Cobwebs in buildings and condensation on the underside of roofing are signs are poor ventilation. A good supply of fresh air is essential to maintain good ventilation within a shed. But make sure the airflow is above the level of calves, as animals kept in drafts will not perform and are actually at higher risk of disease.
“Alongside poor ventilation, high levels of humidity allow pathogens to persist in the environment and spread from calf to calf. Humidity can be reduced by ensuring good drainage and minimising standing water in the environment.”
Mr Potter adds that the vaccine available, if used correctly in combination with management and environmental changes, can also bring about significant reductions in the number of cases of BRD.
“Vaccination programmes need to be tailored to the circumstances on individual farms, so work with your vet to identify the pathogens your stock are at risk from and when the high risk periods in your system are.”