Heat treatment and dehulling effects on feed value of faba beans (OK-Net Ecofeed Practice abstract)

Summary

Reducing antinutritional factors would allow a higher inclusion of pulses in feed rations. Adding a simple treat-ment would increase feed inclusion, product value and reduce the need for imported protein. High tannin bean varieties are already used for human consumption and ruminants. TIA and tannin removal make them better suited to monogastric diets and would improve markets for all bean varieties.
• Samples of Beans were heated to 150oC for 15 minutes in a conventional electric oven (Picture 1).
• Beans were also dehulled manually and through separation from the bulk sample (picture 2) and were sent to an independent laboratory for analysis (Sciantec, UK)
In order to assess benefits for monogastrics, analysis included Crude Protein, Trypsin Inhibitor activity and ami-no-acid make-up of the untreated, heat treated and dehulled beans.
• The test showed that dehulling increased crude protein by 6.66% but increased TIA by 112.5%
• Toasting increased Protein content by 2% but reduced TIA by 37% (pictures 3 and 4)
The test has shown that dehulling can increase protein content but doesn’t reduce trypsin inhibitor activity, but heat treating does, combining the two has the potential to allow increased inclusions of beans into rations. Nei-ther treatment affects amino acid contents.
• Tannins are the antinutritional factors that are most detrimental to pig nutrition.
• Current recommendations are for inclusions of up to 10% beans in sow rations and up to 20% for growing and fattening pigs, although up to 30% has been used successfully where low tannin varieties are used.
• For poultry, TIA is more detrimental than tannins though both are important.
• Inclusion rates of 5-7% beans are common in poultry rations but where beans are processed (heated, de-hulled, extruded or pelleted) to increase their digestibility it is possible to increase inclusion up to 25%.
Faba beans need to be rolled or milled prior to being fed so additional processes can be added into the handling system. Processes such as micronizing (infra-red heating) and steaming are practised but are not practical on an on-farm situation. Heat treating equipment, such as augers fitted with heating elements, are common in USA and Europe for toasting whole soya beans. These systems could be employed with on farm mills in the UK with stored, untreated beans being processed prior to milling.
Dehulling Equipment is available for other grains and can be adapted for beans.
Note: conventional batch or continuous flow grain driers do not increase temperature sufficiently to affect tryp-sin inhibitor activity.