Salmonella Season

down cow

With the start of Autumn, comes the start of another season for the risk of salmonellosis in cattle and your staff. Last year we saw several large outbreaks across Southland and the West Coast of Salmonella Typhimurium in dairy cows ranging from early January to late April. The outbreaks were estimated to cost between $15k - $130k in the form of cows that died, cows that were sick and required treatment, as well as loss of milk production. In addition, we have seen a few cases of abortion in first calving heifers due to Salmonella Brandenburg in late winter, plus some cases of Salmonella Bovismorbificans causing nasty scour outbreaks in young calves in the spring.

Risk factors for Salmonella Typhimurium outbreaks appear to be:

  • Feeding a pelletised magnesium oxide supplement (associated with 87 % of outbreaks in one survey).
  • Feeding of Palm Kernel Extract.
  • Poor pest control programs, so that pests can contaminate feed sources.
  • Feeding from continuous troughs where animals can eat more than their allocation of contaminated feed.
  • Feed bins that allow cattle to defecate into them.
  • Stress.

Not only does Salmonella affect cattle, but it also is a zoonotic disease meaning it can be passed to humans. Those people at most risk will be anyone with an immunocompromised state or who are pregnant.

There is a very effective vaccine available for preventing Salmonella outbreaks in cattle. It is called Salvexin+B. It involves two vaccinations, at four weeks apart to previously unvaccinated cattle and then an annual booster vaccination. For most herds, the annual vaccination is timed around drying off. In the outbreaks last year, the cost of the vaccine would be repaid if the affected herds only had an outbreak every 15 - 40 years.

Our recommended vaccination schedule for an unvaccinated herd is as follows:

  • April: 1st shot for R2 heifers and whole herd.
  • May: 2nd shot booster for R2 heifers and whole herd.
  • Thereafter, each year the herd would receive a booster vaccination in May (around dry-off) and the R2 heifers would be given two shots in April and May.
  • This schedule may not be exactly best-suited for your farm depending on your risks factors, so it is best to discuss the specifics for your farm in more detail with your KeyVet.

The vaccine can be used in the face of an outbreak but will take around 10 days to take effect. It is best that it is not given at the same time as any other vaccines or treatments such as lepto/7in1 as this could decrease the efficacy of either product. The vaccine can cause a drop in milk production, which is why we recommend the annual booster to be given around dry-off when the udder is starting to involute anyway. Some early trial work has also shown that vaccination close to dry-off can increase antibody levels in colostrum at calving, leading to increased protection for your calves too.

Give yourself some peace of mind and talk to your KeyVet about Salmonella management in your herd.

- Joel Hughes


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