At this time of year, pasture can be heavily contaminated with lungworm larvae. The warm and wet weather that has dominated the year so far has created ideal conditions for lungworm survival.
CALVES AND PASTURE MANAGEMENT
Calves are very susceptible, particularly if they graze pastures previously grazed by older animals. Faecal samples will confirm any suspicions of lungworm.
Pasture management, whereby calves are turned onto low-risk pasture at this time of year, is vital for lungworm prevention.
A well-designed dosing strategy is also important. Calves need a certain level of exposure to build up their immunity, but they need to be dosed regularly so that worms do not cause clinical disease. It is a very delicate balancing act, so consult with your vet, who will devise a dosing strategy tailored specifically to your farm.
IMMUNITY IN CATTLE
Cattle in their second grazing season can be very badly affected. If they were dosed too often as calves, they may have a very low immunity developed to lungworm. Then, when they enter pasture with a high level of lungworm larvae, the response can be quite dramatic - coughing and difficulty breathing can develop overnight.
Your vet should be called and these animals should be treated immediately. They should be monitored very closely, as death can sometimes occur.
COWS AND GRAZING
Cows, especially dairy cows, can display signs associated with lungworm at this time of year. A drop in milk yield (sometimes up to 2l/head/day) and coughing are often seen.
Cows are being asked to graze lower grass covers and are revisiting paddocks as soon as 17 or 18 days since the last grazing.
This, combined with humid weather, leads to very high levels of lungworm larvae in paddocks.
A bulk milk sample can be checked for antibody levels to lungworm and faecal samples can be analysed.
A lung wash can also be performed, and is a more accurate diagnostic tool. If lungworm is diagnosed, they should be treated with an wormer that has a zero milk withdrawal.
Low levels of immunity can also be an issue. If this is the case, there is a live lungworm vaccine available. You should always talk to your vet before using this vaccine.
IBR infection is often blamed for causing cattle to cough at this time of year. Usually though, IBR will not just cause coughing alone.
The infected animal will run a very high temperature, will have a discharge from both nostrils and will be breathing heavily.
Once an animal becomes infected with IBR, it is infected for life. The virus hides out until the animal becomes stressed and then it comes to the fore.
Often, if cows or calves are affected by lungworm, IBR can take hold as a secondary infection.
There are a number of vaccines available against IBR. A vaccine programme can be devised specific to your farm by your vet.
Copper deficiency has been linked to lower levels of immunity to respiratory diseases.
Soils that are high in molybdenum bind up copper, which results in very low levels being available to grazing cattle. Cattle can develop a dusty brown tinge to their coat and their ability to thrive will be affected. If you suspect copper deficiency, blood samples can be taken.
Don't ignore any groups of cattle that are coughing. Murky misty mornings or dusty feed won't cause them to cough. If an animal is coughing, then there is some disease process at play.
Consult with your vet immediately to avoid any losses. Quick action will get rid of the chorus of coughing and let you get back to the much more enjoyable - and much less expensive - dawn chorus.
Eamon O'Connell is a vet with the Summerhill Veterinary Clinic in Nenagh, Co Tipperary