Energy and Cost Efficient Pretreatment Method Using a Rotary Compression Unit Increases Starch Digestibility, Gain Efficiency, Porosity and Total Liquid Uptake of Feed Grains


Executive Summary

Corn is the main source of energy in broiler diets in the United States. Sorghum grain is generally regarded to have a lower energy value than that of corn. Thermal treatment of broiler feed improves its nutritional value, which may be attributed to gelatinization of starch, degradation of heat-labile anti-nutrients, destruction of cell walls, etc. However, high temperatures during processing may result in Maillard reaction products, reducing lysine bioavailability.

Enginuity Worldwide has developed the process technology of the Rotary Compression Unit (RCU). The RCU has proven to be an efficient method to dry and upgrade lignocellulosic biomass. While processing fibrous materials, it was observed the RCU also has an effect on grains, providing improvement for livestock feed. The RCU is an elegant technology that uses a novel screw and barrel design, with no external heat source or boiler system to heat treat / dry material. The process uses mechanical forces to compress materials and increase pressure and temperature. This results in a process similar to steam explosion of the material without the addition of heat or external steam and minimal energy usage.

The objective of this project was to use the RCU technology to treat grain sorghum at various temperatures. The sorghum’s nutritional characteristics were analyzed using a poultry broiler feed study and bench top analytical methods like SEM imaging, measuring starch degradation, neutral detergent fiber (NDF), lipid, ash, resistant starch, soluble starch, and free glucose. These data were analyzed both technically and economically to identify the impact the processing of sorghum has on the feed quality and value.

The results of the feed study were contradictory to historic sorghum growth studies. During this feed trial improved growth performance was observed in broiler chicks fed sorghum compared to corn. This contradicts previous studies which observed impaired growth performance of broilers fed sorghum as an alternative to corn. It is believed that the varietal selection for sorghum, a yellow endosperm variety (DK 37-07), with high starch digestibility is expected to support broiler growth performance equal to or greater than that supported by corn-based diet. Because of the superior variety, the heat treatment of the feed did not affect chick growth performance or TME of sorghum grains. It is encouraging to note that RCU processing of the sorghum did not decrease bioavailability of sorghum amino acids, based on chick growth performance. Based on pervious chick growth performance and TME measurement of unheated sorghum, the question is how much improvement of untreated sorghum was possible with this sorghum variety? The effect of processing using RCU technology should be tested on other sorghum varieties, or commodity sorghum, that have been measured to be more limited in energy content and starch digestibility. It is our conclusion that RCU processing has potential to improve nutritional value of sorghum grain.

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