Lupins: A real rival for the soya bean
By Emma Penny
NEW, higher-protein lupin varieties, coupled with processing that boosts bypass protein, could make the crop a suitable replacement for soya bean meal in animal rations.
"Latest research shows lupins are a viable nutritive alternative to soya on UK farms," says ADASs Angela Moss, based at the Feed Evaluation and Nutritional Sciences unit at Stratford-upon-Avon, Warks.
Work funded by MAFF and the Milk Development Council on lupin varieties grown in the UK has revealed a difference between current commercially available varieties and newer types now being trialled.
"Early research showed that UK determinate types, which are fairly upright in their growth habit, have different protein profiles, and are probably lower in rumen degradable protein than more bushy types grown in Australia and the US," she says.
However, Dr Moss found that new dwarf, upright types – also known as dwarf determinates – currently in trials produce a higher-protein seed.
"Proteins were also less degradable than conventional determinate varieties. This is because proteins in dwarf varieties have a larger molecular size, and so are less easily accessed in the rumen by rumen micro-organisms, so more is bypassed." Dr Moss says lupins are always considered an alternative to soya bean meal, but are often criticised because they contain less bypass protein.
"New dwarf, determinate varieties dont match soya bean meal, but they do contain more bypass protein than other lupin types."
While soya bean meal contains about 45% degradable protein – with 55% bypassing the rumen – dwarf, determinate lupins contain 55% degradable protein, with 45% bypass protein.
"But lupins could be processed to provide similar amounts of bypass protein to soya bean meal," says Dr Moss. "We are looking at processing, including coarse grinding, extracting oil – lupins contain 10-11% oil – to feed as meal, and heat treating to make protein less soluble in the rumen, so increasing bypass protein." *
• Home-grown protein.
• Dwarf determinates promising.
• Trials now under way.