Animal feeds and dry pet foodsThe main animal feed types are compound feeds. These consist of a variety of blended ingredients, the composition of which depends upon the type and age of the animal but typically include ingredients such as cereals, animal and vegetable proteins, fibre sources, minerals and supplements such as vitamins, veterinary ingredients and other additives. Some of the ingredients are by-products of the food processing industry.
The raw materials are received at the feed mill and may be pneumatically conveyed or mechanically transferred to bulk storage silos. Some small ingredients which may be mixed in during the process, such as supplements, may be sent pre-bagged in appropriate quantities.
Ingredients are weighed (automatically in modern plants) and transferred to holding bins prior to grinding, typically using hammer mills. After grinding the ingredients are thoroughly mixed and any supplements added. The blend may then be drawn off as “meal (mash) feed” or pressed to produce pelleted feed. More commonly, the blend goes on to be manufactured into feed pellets. Steam is injected into the feed in a process known as “conditioning” before being forced through holes in the die (extrusion). The resulting pellets vary in size depending on the intended use. After this stage of manufacture the pellets are dried and then cooled, typically in coolers in which the pellets enter from the top and cool air is blown in from the bottom. The product is also dried as a result of the cool air. To account for moisture loss during pelleting, drying and cooling, water may be added at the blending stage with some feeds. The pellets are then either stored in bulk or packaged. Some feeds may be coated in fat prior to packing.