BVD Control: Why One Measure Isn't Enough for NZ Herds
Bovine Viral Diarrhoea (BVD) remains one of the most significant infectious diseases affecting New Zealand dairy herds.
What are the main clostridial diseases in New Zealand?
The clostridial diseases that are most likely to affect stock under New Zealand farming conditions include tetanus (often contracted at tailing), pulpy kidney (enterotoxaemia), black disease (triggered by migrating liver fluke), blackleg (caused by bruising) and malignant oedema (resulting from fighting).
Sometimes, especially in lambs grazing specialty finishing crops, Sudden Death Syndrome can cause death. Even more rarely, a number of other clostridial bacteria can also cause disease and death and these are covered with a 10-in-1 vaccine. Prior to the use of multivalent vaccines, clostridial death was common and often killed large numbers of stock. The recent trial highlights that clostridia are still around, still cause disease and can be controlled with vaccination.
How are clostridial diseases spread on farms?
Clostridial bacteria naturally exist in the environment and multiply in low-oxygen conditions, such as those caused by bruising. They are ingested with soil or plant matter and often lie dormant in muscle or the gut, awaiting suitable conditions.
How often should you vaccinate for clostridial diseases?
Ewes and cows require annual boosters to protect them and to bolster maternal antibodies which are passed to their lambs and calves respectively, through colostrum.
Young animals need a primer followed by a booster 4-6 weeks later. If they are to graze crops, ensure a booster is given within 3 months of going onto the crop. Rams should also be vaccinated, at least 8 weeks prior to their risk period, which is tupping (because of bruising due to fighting).
What are the early signs of clostridial diseases?
Typically, no early signs are evident, just sudden death. However, with tetanus, lambs may be found lying in a stiff sawhorse position and spasm when touched.
What are the benefits of vaccinating pregnant ewes?
Annual vaccination protects ewes during lambing. She isn’t giving birth in a clean hygienic environment, so the vaccine boosts her immunity to protect her during this stressful time.
It also provides short-term protection via colostrum for their lambs.
Are there on-farm practices that can help reduce the incidence of clostridial disease?
Prevention is key, including minimising bruising during yarding and handling.
Maintaining hygiene with clean, sharp needles and clean docking equipment reduces infection risk, and the gradual introduction of lambs to crops helps prevent digestive imbalances.
Vaccination with clostridial antigens (5in1 vaccine) stimulates the immune system against these diseases.
How do you create a vaccination plan with an unknown flock history?
Assume the flock is unvaccinated and administer two vaccinations 4-6 weeks apart, followed by annual boosters as usual.
Is vaccination costly?
Compared to stock losses, a vaccination program for clostridial disease is far less expensive.
A recent field trial with Ultravac 5-in-1 in New Zealand showed that vaccination of lambs at docking and pre-weaning prevented 23% of the total lamb deaths and returned a gross income more than 3 times the vaccine cost.
For farm specific clostridial disease programs or to learn more about the importance of robust animal health programmes, vaccination timing and the potential harmful consequences for stock when vaccination isn’t given, get in touch with your local vet.
• Article provided by Zoetis
