Efficient mixing is the key to good feed production.
The feed will not be the balanced formulation it is designed to be unless it is properly mixed. Dry mixers are a mechanical means of achieving this and come in two main types - vertical mixers and horizontal mixers.
The vertical mixer (illustrated on the right) consists of one or more vertical screws which elevate the ingredients to the top of the mixer where they fall by gravity to the bottom, to be mixed and re-elevated.
Vertical mixers are the most common type found in small livestock feed mills. However, the vertical type is less well suited to aquaculture, poultry and fish feeds than the horizontal type, which are much more efficient in blending in small quantities of liquids (such as added lipids) or in mixing ingredients with different particle sizes.
Horizontal mixers consist of a series of paddles or metal ribbon blades mounted on a horizontal rotor within a semi-circular trough. The blades move the material from one end of the mixer to the other, tumbling it as it goes. These mixers usually discharge the mixed product from the bottom, using the same mixer blade action. See above for inside views of both a paddle mixer and a ribbon mixer.
Another type of mixer, which is similar to the horizontal type in action, has a bowl-shaped or flat-bottomed container in which a series of paddles are mounted on a spindle driven by a motor mounted either above or below the mixer (See pictures below). This type of mixer has the same advantages over the vertical type of mixer as the horizontal mixers mentioned earlier. In addition it is cheap and is therefore frequently used in farms, particularly in South East and South Asia. It can also be used for mixing moist feeds.
Mixers (For wet feed ingredients)
Vertical mixers are unsuitable for mixing wet ingredients. Horizontal mixers are more suitable but, because of their complex construction, are often difficult to clean properly. There is also a tendency for sticky materials to adhere to the blades and to accumulate at one end of the mixer. Simple bowl or circular mixers, pictured above, are the most suitable types for mixing wet ingredients or mixtures of wet and dry materials. They can also be used for mixing dry ingredients. This type of mixer is available in sizes suitable for mixing a few kilograms or of dealing with several tons of ingredients. The larger types discharge the mixed product from the bottom.