Cake meal is the residual part of oilseeds after extracting most of the oil, including soybean cake, peanut cake, cottonseed cake, rapeseed cake, sesame cake, sunflower cake, or meal. This kind of feed has high crude protein content and is the main protein source in fish feed. In recent years, it has been widely used to replace expensive fish meal in fish compound feed with good effect. However, this kind of feed generally has the following shortcomings: 1. Low methionine content, more phosphorus and less calcium, lack of carotene, etc. ②It contains some toxic substances, which affect its palatability and digestibility. ③ In the case of excessive heating, the protein will be denatured and the protein digestibility will decrease. For safety reasons, the following precautions should be taken when using cake meal in fish feed:
1. Because of the harmful substances such as antitrypsin, the raw soybean meal has poor palatability and low utilization rate of feed protein. It should be used after proper heat treatment (110℃, 3 minutes).
2. Cottonseed meal contains gossypol and other harmful substances. Note that the proportion of adult fish feed should be controlled below 30%, and the amount of cottonseed meal in parent fish feed should not exceed 5%. When the proportion in the adult fish feed exceeds 15%, it must be detoxified before use. There are many methods for detoxification of gossypol, such as cooking method, alkaline water soaking method, ferrous salt method, yeast fermentation method, etc. Among them, ferrous sulfate method is the most simple and thorough. The amount of ferrous sulfate added is generally the free gossypol in cottonseed cake. 5 times the content.
3. Rapeseed meal contains a series of toxins or anti-nutritional factors. In order to improve its use effect and avoid poisoning, it is generally used in limited quantities (the dosage should be controlled below 20%) and strengthened with matching (used in conjunction with fish meal and bean cake) or adding Lysine. When the dosage is large, it should be detoxified. At present, the method of burial or fermentation is generally adopted, and it can also be detoxified by soaking in organic solvents.
4. Peanut cake contains antitrypsin, so it should be heat-treated before use. Generally, the antitrypsin is controlled at about 120℃. Shelled peanut cake has low crude protein content, high crude fiber content and low feed value, so it is not suitable for carnivorous and omnivorous fish, and herbivorous fish are also limited in use.
5. Sunflower cake has good palatability, and the quality of shelled cake is comparable to that of soybean cake, and it is non-toxic. The content of calcium, phosphorus and vitamin B group is higher than that of soybean cake, so it is an excellent protein source in fish feed. However, the shelled sunflower cake contains a lot of lignin, which not only makes the crude fiber difficult to digest, but also reduces the digestibility of nutrients. Generally, the dosage should be small, and it should not be used as meat and miscellaneous fish feed.
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