Guidelines for Managing BJD in Cattle Saleyards

1. Risk Assessment

The relevant features of Johne's disease and the causative bacteria, Mycobacterium paratuberculosis include:

• Johne's disease occurs in cattle in south-eastern Australia.
  
• Most of the infected herds are not officially known to be infected but have a Non-Assessed status and are free to move cattle to sale within their zone.
  
• Dairy and dairy-cross cattle present the highest risk of being infected.
  
• The infection is uncommon in pure beef cattle.
  
• Infected cattle are usually older than 2 years of age before they start to excrete bacteria.
  
• Cattle with advanced infection are particularly potent sources of bacteria.
  
• Cattle are most susceptible to becoming infected as calves.
  
• Calves are inquisitive and often lick and suck surfaces and materials.
  
• Cattle over about a year of age are relatively resistant to infection.
  
• The bacteria can survive for months in the environment.
  
• Survival of M paratuberculosis in the environment is affected by high temperatures and sunlight, so shade and cool conditions favour survival.
  
• M paratuberculosis dies off more quickly in material containing urine and ammonia.

Survival of the bacteria in saleyards

Hosing can remove the vast majority of faeces, and therefore M paratuberculosis, from a hard surface. Drying and exposure to sunlight should reduce contamination further. The survival of M paratuberculosis may also be reduced by lime, so concrete surfaces may have a similar effect.

Once a shaded, soft-floored pen environment is contaminated M paratuberculosis, bacteria are likely to survive for considerable periods compared to an outside pen that can be hosed out and is exposed to the sun. (It is worth noting that, although contamination is likely to be higher in cattle barns housing infected cows in Europe and North America than in Australia, calves in such environments are easily infected.)

Although shading of the sale pens would favour survival of M paratuberculosis, ammonia from urine and heat generated by the decay of organic material on the floor may help kill it and reduce contamination.

If the roof keeps the floor relatively dry, without being dusty, the bacteria may not be as easily transmitted as on a wet and boggy surface.

2. Risk Management

The key point to managing the risk of spreading Johne's disease among cattle at a saleyard is not putting calves under 12 months (excluding vealers going direct to slaughter) in pens that are contaminated with adult faecal material. This includes faecal material spread mechanically, by equipment and boots.

Given the points above, the risk of spreading BJD at saleyards should be reduced by:

• Having dedicated pens for calves up to 1 month of age.
  
• Having dedicated pens or pens that are cleaned out and, where appropriate, covered with new material before use for calves from 1 to 12 months of age.
  
• Cleaning up calf pens after each sale.
  
• Walking calves quickly along laneways contaminated by adult cattle.
  
• Avoiding moving calves along laneways contaminated with faeces by high-risk cattle mentioned in the following dot point.
  
• Having dedicated pens that are used for:
  • aged culls;
    
  • abnormally thin cows and bulls (taking into consideration drought etc); and
    
  • adult dairy cattle.
• Cleaning up any areas of gross faecal contamination after each sale.
  
• Preventing drainage of faecal material or pen washings from adult pens into calf pens.

Breeding cattle are the main ones that spread Johne's disease and risk management should be tightened for any breeder sales that are held at the selling centre.

The Australian Johne's Disease Market Assurance Program for Cattle (CattleMAP) includes additional guidelines to protecting MAP status at sales and exhibitions.

Page Updated: 1 July 2005