DairyNZ principal scientist John Roche issued the warning as dairy farmers across the nation reported a greater incidence of milk fever.
High dietary levels of phosphorus reduced the effectiveness of vitamin D in helping the cow absorb calcium, and feeds that are high in phosphorus should be minimised in the run-up to calving.
This would include silage or hay made from paddocks that get a lot of effluent, or supplements from by-products like PKE, wheat middlings, and wheat or maize distillers' grains .
He said feeding cows palm kernel was one of many risk factors for milk fever, which occurs because of low blood calcium and usually happens before or after calving.
"If you have a milk fever problem and are feeding PKE pre-calving, you need to consider that it may possibly be contributing to the problem," said Dr Roche.
Other triggers for milk fever could include breeding -- jersey cows are five times more likely than holstein-friesians to fall sick -- or cows which are too fat or too thin.
Illnesses or dietary restrictions or even a difficult calving could also trigger the illness, which can cause a cow to lose condition and have difficulty standing.
Dr Roche said the most important way for preventing milk fever at any time was through giving each cow 20g of magnesium daily for the two weeks before calving.
Separately, palm kernel has attracted attention from environmental activists critical of rainforest clearance to plant huge areas in oil palms because of the environmental damage -- such as loss of habitat for endangered orangutans -- and the greenhouse gas emissions from destruction of forests,
Dairy company Fonterra has been the subject of protests from environmental activists because its subsidiary, rural services company RD1, imports over one million tonnes of palm kernel extract (PKE) annually.
Chocolate-maker Cadbury tried to introduce palm oil in its local products, but stopped because of criticism for similar environmental reasons.
