Preliminary judgment on the quality of pellet feed for fish

In recent years, with the increasing popularity of high yield @ # @ 233 grains @, full-price pellet feed for fish has been widely used in fishery production. However, because there are many feed brands in the market, and there are great differences in quality and grade, the majority of farmers are unable to judge its quality. This paper introduces a simple method to judge the quality of fish feed by sense. That is, "one look, two smells, three twists, four bubbles, five chews", which can be used as a reference when choosing and purchasing pellet feed.

1. Look

1.1 look at the color: fish pellet feed is made from several main raw materials such as fish meal, soybean meal, cottonseed meal, rapeseed meal, secondary meal, meat and bone meal and so on. To a certain extent, the color of the finished product can reflect the amount of raw materials used. For example, if there are more fish meal and soybean meal, the fish color is slightly yellow; when the miscellaneous meal is more, the material color is dark red; when the secondary powder is more, the material color is slightly gray, and so on.

1.2 look at the particle size: fish feed is a particle formed by granulation process. Through the observation of the particle size, the ratio of the original grain, the crushing fineness of the original grain, the uniform degree of quenching and tempering, the granulation process and the selection of ring mold can be judged. The particle size of high-quality fish feed is uniform and smooth, the section is neat, the length is 1.5 to 2 times of the diameter, and the pulverization rate is not more than 1%. If you observe the particle size of fish, it is found that the particle size is rough, the cross section is uneven, and the pulverization rate is high. it is estimated that the following reasons are: (1) insufficient crushing fineness of raw materials, (2) unreasonable raw material ratio, (3) uneven quenching and tempering, (4) improper selection of ring mold, (5) improper adjustment of cutter distance, and so on.

1.3 look at the luster: the particle surface of high-quality fish feed is smooth, uniform and shiny. This kind of feed has good palatability, good storage resistance and high utilization rate. The surface of inferior fish feed is rough and dull. The above phenomena are mainly caused by the following reasons: (1) insufficient crushing fineness of raw materials, (2) improper compression in the granulation process, (3) insufficient addition of feed oil, and so on.

1.4 look at the submergence speed: when feeding pellet fish feed, it is necessary to ensure that the feed has a certain buoyancy and submergence speed. Fish feeding on the surface of the water body can not only save feed but also facilitate the observation of fish feeding.

General fish feed should be kept floating on the surface for 3 to 4 seconds. If the water is submerged too fast, the fish will not have time to feed, which will cause waste; if the floating time is too long, it will prove that the feed has more crude fiber content and poor quality.

2. Smell

Pellet fish feed is made by steam conditioning and ripening after mixing all kinds of raw materials. When the raw material is aged, it will give off a unique fragrance. Grab a handful of fresh-opened feed and smell it in front of your nose. If it is found that there are moldy bitter taste, scorched taste, artificial fishy taste, raw fish powder flavor and raw flour flavor, it shows that there are the following problems in the processing process.

(1) poor quality of raw materials, (2) excessive moisture, deterioration during storage, (3) inappropriate quenching and tempering temperature, and so on.

3. Twist

Fish feed needs to be transported many times from production to feeding, which objectively requires a certain mechanical strength. In general, you can twist it with your fingers for a few times without breaking it, but not too hard. If a twist is broken, it shows that the feed hardness is not enough, the pulverization rate is high, which is easy to cause feed waste; too hard, poor palatability, affect the movement of feed in the digestive tract, easy to cause the occurrence of fish enteritis.

4. Bubble

By soaking the feed in water, on the one hand, we can check whether the physical properties of the feed can meet the needs of the digestive tract of fish. On the other hand, the general composition of its raw materials can also be analyzed. The specific method is to grab a handful of feed into the water, observe the feed dispersion time, the general feed is completely dispersed after 3-5 minutes, the feed dispersion time is too short, easy to cause fish digestive tract swelling, affect its food intake; feed dispersion time is too long, affect the fish intestinal peristalsis, is not conducive to fish digestion and absorption.

5. Chewing

Although fish feed is swallowed, but the taste is the main factor affecting their feeding behavior. Through the sense of touch and taste of our mouth, we can feel the hardness of the particles and whether there is a peculiar smell, whether the feed has gone bad, whether the feed is mixed with impurities (such as sand, soil, etc.) and so on.