EMS, also known as acute hepatopancreatic necrosis syndrome (AHPNS), is a disease affecting shrimp believed to be caused by bacterial infection.
“EMS can quickly spread among farmed shrimp populations, causing mortality rates of up to 90% within 30 days,” Cargill wrote in its worldwide patent filing. “Therefore, the prevention or mitigation of the occurrence of EMS in shrimp farms is desirable.”
Cargill said a feeding strategy that improved the overall dietary function of shrimp was key in the fight against such diseases.
“To get the full benefit from the diet, the ingredients must be well digested and absorbed by the animal. The best way to achieve this goal is by having a balanced gut pH and gut microbiota, which aid in the digestion of the diet, endogenously produce key nutrients for its host, and fight pathogens. Reducing the pH of the gut and providing key nutrients to the microbiota is the optimum way to maintain a healthy gut environment and maintain the microbial population.”
Organic acid and gut pH
Cargill said its fermented feed did just that because of one key component – organic acid – made from fermenting vegetables, fruits, grains or other plants.
The organic acid component represented between 45-50% of the feed product on a dry weight basis and could be lactic acid, formic acid, citric acid, gluconic acid or salts, among others. Importantly, Cargill said the final feed product had an overall pH of 4.5 or less.
Cargill said feed trials showed its fermented feed reduced pH levels in the gut of shrimp that, in turn, helped the animal build up a resistance to bacteria.
“The results from this study show the nutrition advantages of the fermented vegetable protein feed product in shrimp diets for optimal utilization of the available nutrients in the diet through lowering the gut pH for better mineral solubility, protein hydrolysis, and amino acids and mineral/vitamins transport through the gut epithelium.
“…Without wishing to be bound by theory, the organic acids present in the ingredient seem to improve proteolytic enzyme activity and be available as an energy source to the animals, which alongside the nucleotides and nucleosides from the fermented vegetable protein syrup strengthen the animal’s health condition, reducing the negative impacts of the stress caused by the traditional rearing methods,” it wrote.
Fermenting vegetable matter
Cargill said obtaining the organic acid through fermentation was a relatively easy process that could be achieved by fermenting the content of process streams in vegetable mills or any waste or by-product made there.
Feed manufacturers, it said, could use any wet stream from milling of corn, wheat, sorghum, cassava, or any other grain, pulse or vegetable material.
An ideal fermentation medium, it said, was light steep water – an early by-product stream of wet corn milling – because the stream was high in protein and sugar.
Cargill said once the mill stream had been fermented to increase the concentration of organic acid, it had to be concentrated either through evaporation or applying heat to create a fermented vegetable protein syrup that could be used in the final feed product.
This syrup, it said, could then be blended with several other ingredients, including high-protein corn gluten meal or a corn protein concentrate.
The company said optimal crude protein levels in the final feed ranged between 70-75%: “The use of concentrated protein sources is desirable in aquaculture diets in order to address nutritional needs in a metabolizable nutrient dense package.”
The feed major said that using protein in the mix bound up the organic acid component, which worked to ensure a slower impact in the gut of shrimp.
“This mechanism may be biologically useful as a timed-release technology in the target species, allowing a buffering over time as opposed to acute buffering of the animal’s gut.”
Extra precautions
Cargill said additional processing steps could be made to decrease or eliminate “one or more anti-nutritional factors”.
For example, the process could include a treatment with one or more enzymes like phytase to release bound phosphorus from phytate that created a bioavailable phosphate form for the animal. A hydrogen peroxide treatment could also be used to reduce or eliminate the anti-nutrient sulfur dioxide.
While the fermented feed would be particularly useful to the farmed shrimp industry, it could also be used in poultry and swine, said the company.
Source: WIPO Publication No. WO2017112841
Published: June 29, 2017. Filed: December 22, 2016.
Title: “Fermented vegetable protein compositions and methods for producing the same”
Authors: Cargill Inc – E. Bell, K. Mertz, EM. Peters, F. Soller, A.Woo, HN. Yehia and J. Warminsky