A feasibility study to evaluate mechanical and enzymic methods of improving cereal quality for animal feeds
About this project
The project's objective was to investigate the use of some existing technologies to improve the nutritional quality of barley for use in animal feeds using in vitro techniques. The ability to improve starch and protein digestibilities and increase sensitivity to cell-wall degrading enzymes were measured. Two scenarios were investigated: a comparison of barley-meal pellets produced under conditions similar to those presently used in compound-feed plants (conditioning) with pellets produced by an expansion process (expansion). The second scenario evaluated the potential of cell-wall degrading enzymes as a process aid in the in- house production of liquid feed as practised on some farms.
Although both types of pellets had higher starch-digestibilities than the meal, the starch in pellets produced by expansion not only was more digestible but was also digested at a faster rate by pancreatic amylases. Both production methods reduced protein solubility and made the protein more sensitive to attack by intestinal proteases. However, the increase in protein digestibility was slightly lower in the case of expanded pellets. Processing abolished the increased solubilisation of protein seen when meal was treated in dilute suspension with cell- wall degrading enzymes. While addition of some cell-wall degrading enzymes could bring about a similar, but slight increase in protein digestibility in the meal and conditioned pellets, the combination of expansion followed by addition of enzyme led to a synergistic increase in protein-digestibility. With regard to susceptibility towards cell-wall digesting enzymes, processing had varying effects. Where an effect was observed, it was similar for both conditioning and expansion.
In studies investigating the role of cell-wall digesting enzymes as process aids, experiments were performed with the best performing enzyme identified in the pellet studies. The enzyme was used to treat 40% suspensions of barley meal for l or 2 hours at 20° or 40°C. Enzyme treatment had no consistent effect on protein solubility or digestibility. However, it was generally observed that suspending meal at 40% solids frequently increased protein digestibility.
This project demonstrates the possibility of effectively measuring the effects of a number of processing combinations on nutritional parameters in terms of both time and cost. It has also demonstrated that the desirable effects associated with the use of cell-wall digesting enzymes can sometimes be further enhanced by the process used to produce the original feed.
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