Single screw exruders and their use in animal feed production

Often, animal feed manufacturers wonder about the interest for them to add an extrusion line to their conventionnal equipment.

The main reason in that production technics are changing in animal feeding, and that the commodities issued from intensive production must satisfy in consumers new demands about their nutritionnal values and their safety. There is also the occasion in the design of classical feeds to use new vegetal crops that must withstand technological treatment to improve their digestibility for the animals they are going to be fed, and/or eliminate toxic and antinutritionnal factors.

Therefore extruders are matchless tools, allowing instant thermic treatment High temperature-Short Time (HTST), the kind of treatment applied to stabilise full fat milk and permit its storage during several months at room temperature without any alteration.

Reluctance of the feed manufacturers to set up an extrusion line in their factories can be sumsummed up as follows :

High cost for the initial investment ;
High operating costs
Low ouputs
To small quantities of products susceptible to be extruded ;
Difficulties to recruit and teach operating people ;
Difficulties to select an extrusion technique : dry or wet extrusion, steam injection, liquid injection, preconditionning, etc…
First applications of extruders in animal feeds were developped for pets and fish, mainly with extruders aimed at producing human commodities . They were made with elaborated high cost twin screw extruders.

However, in the 1880’s, new single screw extruders were elaborated, not so expensive, modular, robust, very flexible, one of those being dry extruders very usefull for the thermic treament of oil seeds (full fat soja). Technologies behind this new equipment leads to the breaking of cellular walls of grains and seeds, leading to a better penetration of the digestive enzymes in the intestine, increasing digestible/metabolisable energy content of the feedstuffs. By the same token, caecal indigestible is reduced, leading to a better litter control an deceased pollution (aquafeeds).

HTST treatment inside the barrel of the extruders (up to 180°C), followed by a sharp decrease at the outlet of the barrel leads to protein insolubilisation without decreasing protein digestibility (no browning Maillard reaction), kill antinutitionnal molecules and toxic substances. The same with enzymes of the raw ingredients (lipase ans lipoxydase, myrosinase), that can affect the product during storage after extrusion, (oils and fats oxydation).

Investment costs | Operating costs | Our Goal

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