Farm Newsletter Jan 2004

IBR – Infectious Bovine Rhinotracheitis

This disease seems to be alarmingly common at the moment. Lee cannot recall having seen such a concentration of outbreaks. The strain that is about at the moment seems particularly virulent.

We have been seeing three main syndromes.

1. Pneumonia in calves.

The virus was killing neonatal calves in one dairy herd recently. Vaccination with the live vaccine that goes up the nose (Tracherine) stopped the problem almost overnight. The vaccine can be used from birth and one shot lasts for at least a year.

2. Milk drop and poorly cows.

Some farms are finding groups of similar aged animals will go off colour, eat less and experience sudden milk drop. They usually have a high temperature and may, but not always, have a nasal discharge and a cough.

Other dairies are presenting us with the odd animal that shows the same signs but no pattern or group involvement seems to occur. Antibiotics and Finadyne or Steroids seem to buck these animals up in both situations, but recovery and return to milk can be terribly slow.

3. Poor conception rates.

One beef suckler herd and three dairy herds have experienced this. All farms had previously had reasonable fertility. The beef unit was a truly closed herd with a bull with an excellent record of fertility. The dairy units used AI with bulls to tidy things up. Suddenly, in mid-autumn, scanning at 30–40 days revealed seemingly endless empty cows. Bloods were taken from the beef animals and tested for IBR (the farm vaccinated for Lepto and BVD) and sure enough, antibody levels were very high indicating recent infection. Bulk milk samples were taken from the dairy units. High levels of antibody to IBR were found in the milk.

Three of the farms have started vaccination programmes.

The disease is highly infectious and contagious. It can also infect, and be spread by, deer, goats, and pigs. The main sources of infections are nasal, vaginal, and preputial discharges, semen and foetal fluids. Generally there is a need for close and sustained contact between animals which explains why the disease is often slow to spread within and between groups. It can often take 2 – 5 weeks to spread in a group. Incubation is about 10 – 20 days. Poor conception rates can go on for months and months!

Hired and bought in bulls should be tested for this disease if you don’t vaccinate the herd. However, even this is not 100% failsafe. It is a Herpes virus – like the cold sore virus in humans. An animal can be infected but the virus can become dormant rendering the cow ‘latently infected’. The animal will test negative but could start shedding IBR virus when stressed (for example when it calves or if it is moved).

As I write this Lee has just come in from a routine visit. Whilst eating a number of Quality Streets he got highly excited about the effectiveness of Tracherine in improving the conception rates in the cows in one of his infected dairy farms. 80% of vaccinated cows scanned positive. 15% of unvaccinated cows were positive. The results speak for themselves.

Barbara Bradley’s Christmas message.

Integrating newly calved heifers into the main herd can often be a problem. They frequently get bullied. Babara has recently started sprinkling their heifers with malt vinegar. She does it once only and the cows hate the smell so much they leave the heifers alone and don’t go near them. During this anointing Chris usually goes out and gets her a bag of chips.

Heifers are affected by so many changes at the time of calving that it’s a wonder any survive! Theses changes include:

• Change of diet
• Change of floor surface (often grass to concrete)
• Change of housing (sometimes their first introduction to cubicles)
• Change of social status. Mixing them with cows puts them at the bottom of the social order
• Reduced dry matter intakes
• Reduced hoof growth at the time of calving, but INCREASED WEAR
• Reduced competence of the immune system, making them much more susceptible to whatever new diseases they are exposed

Can you do more to acclimatise your pregnant heifers to the adult herd environment?

If cubicle training is not possible during their second winter can you house them for a few weeks during July and August when the milking herd is still out? This will also protect against Summer Mastitis.

For the one to two weeks prior to calving, heifers should ideally be fed part of the production ration – enabling the rumen to adjust to the new diet. This will reduce the risk of acidosis and laminitis. Do watch that they don’t become over fat.

Some farmers even walk heifers through the parlour every day thereby overcoming another hurdle.

Look after your heifers – 40% of all heifer calves born alive fail to calve a second time!