Novel animal feed binder from soybean hulls -evaluation of binding properties

The physical properties, especially water stability, of aquatic animal feed are important components of feed quality. Novel feed binders from soybean hulls (SBH) were developed to further improve water stability of the compound feed. Three (SBH) -based binders were evaluated as binding agent (2%) against three natural control binders (carboxymethyl cellulose (CMC), corn starch (CS) and wheat glucan (WG)) with respect to water stability and nutrient leaching after being immersed in water up to 48 h at two water temperatures (22 °C and 28 °C). Pacific white shrimp, Litopenaeus vannamei (mean weight of 6.08 ± 0.04 g) were fed in triplicate aquaria with the experimental diets at a rate of 4% of body weight per day, four times daily, for 6 weeks in a recirculating water system. Diets with SHB had significantly improved pellet water stability compared to the diets with control binders (CS and WG) after being immersed in water for longer than 12 h. CMC had the poorest water stability at 3 h and longer water immersion. Recovery of pellets with soybean hull binders was significantly higher than the pellets with control binders at 24 h of water immersion. After 48 h of water immersion, only diets with SHB were recovered ranging from 30% to 40%. Increasing water temperature resulted in a corresponding decrease in water stability of all pellets. At higher water temperature, however, water stability of pellets with control binders were significantly lower compared to pellets with SHB. The binder that best retained crude protein in all time periods was SHB-3. However, it was not significantly different from other soybean hull binders. Percent lipid remained unchanged in all leached pellets up to 12 h of water immersion and increased afterward. Percent ash of the leached pellets increased at 3 h of immersion and continued to increase with the increasing period of water immersion. Diets with SHB retained higher nutrients than the diets containing control binders after being immersed in water 3 h or longer. Weight gain and survival of shrimp fed diets with control or SHB for 6 weeks were not significantly influenced by binder type. In summary, the SBH-bound pellets were more water stable than the control binders and can produce better and be less expensive natural alternatives to conventional binders.