Currently, most cultured fishes are fed through compound fish feed for economic and social benefits, as a consequence, fish taste and output, to a remarkable extent, are dependent on the quality and production capacity of fish feed. According to the conclusion drawn by fish cultivation experts, within certain limits, the higher the quality of fish feed and the lower the feed coefficient, the higher the growth rate and yield of fish. Meanwhile, the higher the feed conversion ratio, the less waste into the environment and the better the water quality, all of which make the health condition of fish better, decrease the disease risk of fish lower the disease degree of fish, and finally enhance the meat quality and taste of fish.
In general, the key factors that influence extruded fish feed quality and production capacity include raw materials of fish feed, ingredients of raw material, feed formulation design, manufacturing process, and feed-producing machines. Additionally, the subsequent rationality of process design, conveyor operation, grease spraying control, and cooling effect also affect the extruded aqua feed quality. In order to get eligible extruded fish feed, producers need to proceed with the overall administration and proceed from the whole fish feed production line situation, highly efficiently ensuring product quality stability in time.
Key Influence Factors of Fish Feed Quality & Output
1. Raw materials for producing fish feed
Fish feed raw materials, one of the primary factors of feed production quality control, have a wide range of sources, complicated various components, and great differences, mainly including protein feeding stuff, energy type feeding stuff, mineral substance feeding stuff, and feed supplements. All the physical properties of raw materials, including volume weight, granularity, moisture and impurities content, and so forth, can have an effect on extruded feed yield and quality.
- Volume weight: various materials have different volume weights. Usually, raw materials with small volume weight have high cellulose content that is adverse to extrusion, leading to a small yield. Whereas, raw materials with big unit weight can absorb water much better for large output.
- Granularity: Particle size has three types, coarse-, medium- and fine-size, and the latter two are easier to extrude. That is because a larger surface area is in favor of heat and moisture absorption and is easy for gelatinization, and when the fineness of pulverization is fine, the density of materials will be large, hence promoting the quality and output of extruded fish feed. In a word briefly, the particle size distribution of feed should be basically even (without large size), so as to produce extruded feed with good appearance and quality and high production.
- Moisture: Water content in the raw material is closely related to fish feed quality, processing stability and extruding state within the extrusion chamber. No matter moisture is too low or too high, energy consumption is so high that production is also down.
- Impurities content: Too many impurities content in raw materials would have a strong impact on machine abrasion, so the less impurities content, the better.
2. Formulation of fish feed
Fish feed formulation is the basis of how to add a variety of raw materials during the process of feed, so whether the formula design is scientific has a direct close relationship with the quality of fish feed. As the two main nutritive indexes of fish feed, the higher the protein and fat content, the lower the feed coefficient and the better to digest and absorb. However, extruded fish feeds with the same content also have greater differences due to different existential states and structures of feed active ingredients. Taking barley, oat, and wheat for example, carp has diverse protein digestibility of these three grain feeds, obviously “Barley is greater than oat while oat is greater than wheat” mainly because the protein quality of wheat is worse than that of barley and oat, namely, wheat has lower lysine and threonine content.
On the contrary, if the necessary nutrient content of fish feed is too high, it would cause indigestion. For instance, even though the protein content is too much, the protein storage in the fish body is almost constant, that is, the body weight increase is not proportional to the protein content in the feed, which not only leads to waste of protein, but the generated metabolic would pollute water quality. Therefore, there should be a suitable ratio for various nutrient ingredients.
The nutritional requirements of fish for feed have their own features. For example, fish can take full advantage of protein and fat in feed but they cannot make good use of carbohydrates and it’s hard for them to digest cellulose. Besides, different feeding habits of fish may need different nutrition. Hence, the extruded fish feed formulation should be adjusted according to fish feeding habits, and only when nutrient contents match with fish needs, digestibility can be enhanced and the feed coefficient can be lowered. Visit fish feed formulation for more information.
3. Manufacturing process of fish feed
- Materials cleaning: Before entering the extruder, raw materials must be cleaned through screen and magnetic separation, cleaning metal, stone, clod, and other impurities in materials, which can prevent equipment abrasion caused by impurities and increase extruded fish feed production and quality at the same time.
- Materials crushing: Some materials need to be crushed to a certain granularity via a fish feed crusher before entering the extruder. As is well known, a material’s surface area depends on its particle size, the thinner granularity, the bigger surface area, and the faster water absorption, assisting in promoting extruded feed quality and yield.
- Flow of materials into the machine: Materials entering the extruder must satisfy the extrusion need so as to make the extruder work ceaselessly and evenly and ensure the quality of fish feed. If deficiency of materials feeding, the extrusion effect is not ideal while if overmuch materials feeding, it’s easy to cause machine stoppage, leading to a lowering of productivity or even burning down the fish feed extruder.
- Tempering: Before entering the extrusion chamber, materials always need to be processed through steam and moisture, and this pretreatment process is known as tempering which can soften materials for higher plasticity and make materials past-forming for better cohesive action. The 3 factors affecting the tempering system are tempering water, time, and temperature. How much water is added into tempering depends on how much water content raw materials have after crushing but before entering the conditioner, aiming at controlling water content at 19%-25% after tempering. Meanwhile, the tempering temperature should be controlled over 95 degrees Celsius and the recommended tempering time is 20-30 seconds.
4. Fish feed production machine
To produce superior fish feed, in addition to formula, materials, and tempering, feed production machines – fish feed extruder structure design and operation are also quite important influencing factors. To be specific, the screw configuration plays a key role in feed quality, the die head structure should ensure fluid pressure smooth and uniform mixing after passing the die head, the template decides the shape and size of materials, and the slicer mainly has an effect on feed appearance.
As the leading professional fish feed machine manufacturer, we suggest feed plants and fish farmers use high-performance fish feed extruders to produce fish feed. For large scale, choose the extruder with high production capacity, such as 1t/h, 2t/h, or even 5t/h, while for small scale, low production capacity machine is better, including 180kg/h, 300kg/h or 500kg/h and so forth, all of which can make a difference on extruded fish feed yield.
Overall, many factors affect the quality and production capacity of extruded fish feed, and there still will be unpredictable influence factors during the production process, so for the purpose of extruded aquatic feed with high quality and high yield, feed plants and fish farmers who produce feed by own must choose suitable raw materials, adopt scientific formula, lay emphasis on the manufacturing process and use the most appropriate fish feed production machines.