Nile tilapia. (Photo: Terje Engoe)
Rapeseed great choice for feeding farmed fish species
Tuesday, July 05, 2011, 00:50 (GMT + 9)
A by-product of biodiesel can be used in large amounts to feed farmed fish. Rapeseed can serve to make meal into feed for a key global aquaculture species: Nile tilapia.
"The world needs food and the world needs energy. Therefore, it is so exciting to upgrade by-products from biodiesel, in this case rapeseed meal, to a better protein source for fish", said Trond Storebakken, professor at the Aquaculture Protein Centre (APC), a Norwegian Centre of Excellence affiliated with the Norwegian University of Life Science (UMB).
PhD student Youling Gao recently showed that lofty amounts of protein-rich rapeseed meal work very well as feed for tilapia.
"We observed fast growth, efficient feed utilization and found no health problems," Storebakken said, reports Aquafeed.
"Today, tilapia from this breeding program are extremely fast growing, and they efficiently utilise feed based on inexpensive plant ingredients. That’s why we want to utilise the inexpensive rapeseed meal from biodiesel production, that is not suitable for direct human consumption, in feed for exactly this species", Storebakken added.
|PhD student Youling Gao flankert by his supervisors. From right: Professor Trond Storebakken (APC/UMB), Professor Margareth Øverland (APC/UMB), and reserach scientist Jon Fredrik Hanssen (UMB).
(Photo: Olav Fjeld Kraugerud, UMB)
Access to rapeseed meal will rise as demand for its oil for biofuel goes up.
On the other hand, the disadvantage with rapeseed meal as a by-product of biofuel production is that glucosinolates, natural pesticides, are concentrated in the meal. These substances prevent the plant from being eaten by insects and, although not poisonous, are turned into toxins by an enzyme that can be activated during processing.
When APC recently tried to destroy the glucosinolates by subjecting rapeseed meal to solid-state fermentation, the tilapia grew better on this meal than on untreated rapeseed meal. Ruminants can get rid of glucosinolates by allowing microbes in the rumen to ferment the feed.
"Inspired by what’s going on in the rumen, we’re now trying out wet fermentation with two different cultures of microbes. While the first culture of microbes will remove the fiber network that protects the glucosinolates, the next will destroy them once released", said Olav Fjeld Kraugerud, postdoctor at APC.
The use of rapeseed is limited because of glucosinolates and phytic acid, substances APC wants to remove.
"With the large interest we’re seeing on using the oil from rapeseeds to produce biodiesel, the protein is left over and we have to utilise it for food", said Storebakken.
Nile tilapia has been transplanted from Africa to Southeast Asia and South America, where it is a vital species for the aquaculture sector. Norwegian research institutions have been very important tools to facilitate the fish’s production.
By Natalia Real