Sharemilker Nan de Haan considered getting his herd vaccinated against the disease but a vaccine shortage forced his decision.
"I can’t do it if I wanted to, so my prevention measure went out the window," he said.
An MSD Animal Health spokeswoman said the company was out of stock of the salmonella vaccine for sheep and cattle Salvexin +B due to an unexpected manufacturing issue.
No batches of Salvexin +B released for distribution had been impacted by the issue.
Several salmonella outbreaks in dairy cattle in New Zealand had significantly increased demand for the product putting further strain on supply.
"MSD Animal Health understands how critical the supply of this product is to the welfare and production of sheep and cattle and the well-being of the farmers that work with them.
"We are working to resolve this issue as quickly as possible, including working with regulators to determine the feasibility of importation of other salmonella vaccines to bridge the gap in supply, if necessary.
"We anticipate having Salvexin +B back in stock by early June. In the meantime, we are working closely with veterinarians on salmonella mitigation practices and are communicating closely with them regarding updated supply timelines," she said.
Biosecurity New Zealand surveillance principal adviser Jonathan Watts said the salmonella situation in Southland continued to be monitored.
Case numbers for autumn were higher than at the same time in previous years and were continuing to be reported.
A survey on risk factors associated with the salmonella outbreak in Southland was completed in late 2024 and early 2025. The survey was to help understand the risk factors that had led to this outbreak to help mitigate future outbreaks and to reduce the impact of outbreaks in the future. The response rate to the survey was less than ideal, he said.
Survey data was being analysed and a preliminary report was expected later this month.
New Zealand Veterinary Association head of veterinary services for large animals Dr Cristin Dwyer encouraged farmers to speak to their veterinarians to determine the best practical advice for their specific circumstances.
Generalised online advice could be found through websites such as DairyNZ, MSD Animal Health and Beef + Lamb New Zealand, Dr Dwyer said.
