Housing may seem some time away for most farmers, but preparation at this point can avoid significant losses later. Pneumonia is still the number one killer of adult cattle in Ireland and one of the greatest sources of worry for farmers buying or preparing weanlings at this time of year for winter housing.

Pneumonia in weanlings is multi-factorial (many contributing issues) involving the animal, the environment and the various agents that cause lung infections (lungworm, viruses, bacteria and mycoplasmae).

Though much emphasis is placed on the agents that cause pneumonia, it is important to realise that successful disease management will only result from a total control programme.

We will look later at some key points in such a programme before assessing the role of vaccination in control. Lungworm should always be eliminated from the list by the use of an effective anthelmintic dose at housing.

The effects of viruses, bacteria and mycoplasmae can be minimised through the use of some management strategies in association with vaccination.

Medication, using antibiotics, should only be used if no other viable option is available. Fundamentally, control of losses will hinge on executing all the steps in a timely manner necessary to minimise risk.

Weaning

All farmers have their own weaning process varying from abrupt total weaning to staged partial removal of cows. Other management procedures, such as dehorning or castration around this time, should be avoided. Vaccinations should be administered at least two weeks either side of weaning as the stress involved may interfere with vaccine effectiveness. If animals are weaned at grass, creep access to new pasture facilitates the reduction of the calf-cow bond, but it is not always feasible. Ensuring animals are consuming at least a kilo of meal before weaning eases the transition though access to fresh new grass is most important – freshly weaned calves are fickle characters.

Housing

This should be conducted on a dry day on to loose straw-bedding at a low stocking rate. Easy access to water and creep feed is essential to minimising stress by facilitating animals in their new environment. The building should be well-ventilated and lit. Aspects of housing that maximise air-flow (openings at the eaves, spaced sheeting/boarding, apical vents, etc) while avoiding draughts are all significant. Light is also very important – not only to allow animals to find water, feed, but to ensure that the stockman detects disease early. Your local Teagasc adviser or vet will be glad to assist you in measurements and with suggesting improvements. Minimise mixing of groups (especially of different ages) and moving animals between groups or stress to animals prior to housing (transport). Animals are generally purchased in marts at this time of year from a whole range of sources and backgrounds. Some will have been exposed to infectious viruses during the rearing period, while others will be naïve. The stress of transport causes previously infected animals to shed organisms and infect others. When this is coupled with animals housed in a close environment, it is an ideal recipe for a pneumonia outbreak.

A useful way to avoid this is to purchase animals ahead of housing and let the animals out to grass for 10 to 14 days before housing. This allows them to recover from the stress of transport and reduces house-related transmission. It also allows time for vaccination programmes to be instituted ahead of housing as well as appropriate parasite control (lice, worms and fluke).

Different age groups should be housed separately, in different air spaces, as older animals that have been previously infected can shed organisms and infect naïve animals. Stocking density should also be carefully monitored to avoid humidity problems.

Medication

A major change has taken place in the use of antibiotics in the prevention of respiratory disease.

Long acting novel antibiotic injections effective against pneumonia, have recently been licensed for both treatment and prevention. Antibiotics, however, are really only useful in controlling losses in the early stage of a potential outbreak or as a preventative when animals arrive after extended transport.

Their usage should be minimised as indiscriminate use encourages the development of resistance and increases the risk of residue violations.

Any impending outbreak of pneumonia should involve immediate consultation with your vet as he/she is best placed to advise you on all of the treatment options available.

Conclusion

Losses associated with a mild outbreak have been estimated to cost between €50 and €150/head in production losses and medication expenses. Full vaccination at €15 to €17/head certainly pays for itself many times over in the face of estimates like this. Good management, in conjunction with vaccination, will assist in minimising losses. Antibiotics should only be used as a last resort.

Vaccines against pneumonia fall into two broad categories – live vaccines and inactivated products. Dead vaccines are administered by injection and, as a general rule, are slow at inducing immunity. Thus, it is necessary to organise vaccination well ahead of housing. Two injections are invariably required, spaced approximately four weeks apart to give strong and lasting immunity. Viruses still play the biggest role in pneumonia outbreaks and husbandry strategies, coupled with correct vaccination programmes, can effectively reduce the economic effect of this crippling disease. Respiratory syncitial virus (RSV) is probably the most common cause of post-housing weanling pneumonia. It causes difficulty breathing, frothing at the mouth and, in some cases, death.

Clinical disease

IBR is a serious clinical disease, which can give rise to coughing, runny eyes/nose and even death. Weight loss is significant and it tends to become endemic on large units. IBR and RSV are the main causes of viral respiratory disease in weanlings. Parainfluenza virus causes fever, weight loss and mild pneumonia. Its biggest influence is that it makes animals more susceptible to other forms of pneumonia.

Live vaccines administered intranasally give a more rapid onset of cover. Various vaccines are available (Table 1).

Pasteurella (Mannheimia) haemolytica is a common cause of pneumonia in housed cattle due to a stress-related increase in this bacterium in the lungs or secondary to viral infection. If untreated, animals die in a few days.

Only one vaccine is available that contains Pasteurella (Mannheimia) haemolytica.

Mycoplasma is becoming more commonly diagnosed on Irish farms and it may be more common than official diagnostic rates suggest.

It causes mild coughing, ill-thrift and death, if untreated.

There is no vaccine for this latter agent and control depends on improving ventilation and stocking rates and treating with a mycoplasma-effecive antibiotic product.

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