EACH year New Zealand imports about two million tonnes of palm kernel expeller (PKE), a by-product of palm-oil processing in Indonesia and Malaysia, to feed dairy cows, at a cost of NZ$800 million.
But University of Canterbury research has shown PKE contains concentrations of some elements that may be harmful to cows. Professors Sally Gaw and Brett Robinson analysed the chemical composition of several batches of PKE imported into New Zealand over two years.
The professors found it contained concentrations of iron, magnesium and phosphorus that exceeded safe levels for dairy cattle health. Some batches contained concentrations of aluminium, copper, sulphur and potassium within 90% of their safe limits.
“These elements may have both positive and negative effects on the health of dairy cows and soils.
But there is no monitoring, and our research shows the chemical composition of different batches imported into New Zealand is highly variable,” the professors said.
“Copper in PKE may be helpful in treating widespread deficiencies of this element in New Zealand’s farming systems. Similarly, magnesium in PKE may offset the need to supplement this element for lactating dairy cows.
“PKE may be a source of fertilising nutrients into soils. It contains high concentrations of phosphorus, which will improve pasture growth when deposited on the soil in animals’ manure.”
However, the concentrations of iron, aluminium, potassium and sulphur in PKE were thought to cause nutrient imbalances in dairy cows. The actual effects on dairy farms, soils and milk were unknown.
Other evidence suggested these chemical elements, when eaten by cows, could end up in milk.
“Currently, environmental regulations require farmers to quantify every input to their farms in order to meet nutrient budgets to stay within freshwater quality standards. When the composition of PKE changes batch by batch, it becomes very difficult to quantify farm inputs and meet farm-nutrient budgets,” the professors said.
“Fonterra and Synlait, two of New Zealand’s largest dairy companies, actively discourage the use of PKE because it can change milk composition, giving it a higher fat content. However, it remains widely used due to feed shortages.
“Potentially, PKE use could be offset by reusing some of the more than two million tonnes of food and food-processing waste New Zealand produces annually.”
