Rapeseed that is low in erucic acid and glucosinolates is referred to as 00-rapeseed in Europe and canola in North America.

"Breeding programs in North America and Europe have focused on selecting varieties of canola and rapeseed with low concentrations of erucic acids and glucosinolates," said Professor Hans Stein from the University of Illinois.

"We wanted to compare the co-products from the North American and European varieties, as well as determine effects of processing on the nutritional value of the co-products."

Removing the oil from the seeds via solvent extraction, results in 00-rapeseed (or canola) meal left over, and removing the oil via expeller extraction, results in 00-rapeseed expellers.

Professor Stein and his team tested canola meal from North America, 00-rapeseed meal from Europe, and 00-rapeseed expellers from Europe.

An experiment looking at the digestibility of amino acids in the three products showed there was no difference in amino acid digestibility between canola meal and 00-rapeseed meal.

In a second experiment, availability of energy in the three coproducts were determined. As with amino acid digestibility, no difference in energy concentrations between canola meal and rapeseed meal was observed.

"The chemical composition of the seeds from plants grown in Europe and North America doesn't appear to differ despite their different origins," Professor Stein said.

However, differences between 00-rapeseed meal and 00-rapeseed expellers were observed.

Most amino acids were more digestible in 00-rapeseed expellers than in 00-rapeseed meal. In addition, 00-rapeseed expellers contained 7.6 per cent more digestible energy and 7.7 per cent more metabolisable energy than 00-rapeseed meal.

Professor Stein said that the differences in amino acid digestibility and energy concentration were due to the oil remaining in the 00-rapeseed expellers after processing.

"Expeller extraction is less efficient at removing oil than solvent extraction so the 00-rapeseed expellers contained more fat than the meals," he said.

"Fat contributes energy to the diets, and it also slows passage of digesta in the intestinal tract, which allows for more absorption of amino acids."

Professor Stein also cited possible heat damage in processing as a factor that might have reduced amino acid digestibility in 00-rapeseed meal.