Ravensdown spokesman Gareth Richards said everyone was subject to a drug test before starting employment at the company.
The names of all staff were also put into a pool and could be randomly selected to be tested, he said.
Ravensdown offered free counselling to any employees stood down after failing to pass a drug test.
"At Ravensdown, workplace drug testing is a really important part of our safety culture where we work hard to take care of each other.
"And like many other employers in the Hawke's Bay area, we take that health and safety priority very seriously," Mr Richards said.
Justin Courtney of Silver Fern Farms said the company tested for a variety of substances in the employment process.
It also carried out random testing to ensure people were safe in the work environment.
He said employees respected the drug-and-alcohol policy and programme the company had in place as part of its health and safety culture.
Silver Fern Farms has three Hawke's Bay plants - Wairoa, Whakatu and Takapau.
Other results from the detection agency for Hawke's Bay showed 80.3 per cent had used cannabis, down slightly on 80.7 per cent the previous year.
Figures showed 11.3 per cent of positive tests detected opiates, down on 13.8 per cent in 2014.
Nationwide, positive workplace drug tests increased slightly last year on the previous one from 6.14 per cent to 6.19 per cent.
Methamphetamine showed up in 11.8 per cent of positive tests, up on 8.1 per cent in 2014.
The Drug Detection Agency chief executive Kirk Hardy said the methamphetamine problem was not new to New Zealand and there appeared to be a growing supply of - and demand for - the drug.
The trend was similar to the late 90s and early 2000s.
He believed the social impact would be a resurgence of "horrific unspeakable" crimes.
Mr Hardy said there had been a decrease in the overall percentage of positive drug tests in forestry - reflecting a behavioural shift to an intolerance for drugs in such industries.
He said the industry was very vigilant with testing and education programmes.
As well as preventing accidents in the workplace, the industry was addressing issues before they became a wider problem in society.
Mr Hardy said the rate of positive drug tests was also down in the transport industry.
He said it was normal practice for transport operators to have stringent drug-and-alcohol testing and to have TDDA regularly present to members about the dangers of drugs in the workplace.
However, the proportion of people testing positive for methamphetamine was up in both the forestry and transport industries.
The Drug Detection Agency conducted more than 120,000 drug tests nationally in 2015.
