Introduction to compound feed for freshwater pomfret farming
Freshwater pomfret (Piaractus brachypomus) is a feeding fish, and in intensive farming such as ponds, cages and flowing water where freshwater pomfret is the main species, compound feed is used for feeding. This is also an important measure to increase output, promote growth and shorten the farming cycle.
Practice has proved that farming with compound feed has the following advantages:
High nutritional value, suitable for intensive management with fine culture and high yield.
The sources of feed are expanded. Its feed raw materials include cake and meal types, bran types, bean types, distiller's grains and residues, coarse feed and animal feed, and many other feeds.
Feeds with different nutritional compositions can be formulated according to the species and size of the fish, so as to best suit the needs of the farmed fish.
Modern advanced processing technology can be used for large-scale production, meeting the needs of the development of fish farming production.
It is suitable for automatic feeding, improves labour productivity, and is conducive to development in the direction of mechanisation and factory farming.
Principles for formulating compound feed
Although the nutritional requirements of freshwater pomfret have not yet been determined, the general principles should also be grasped when designing and formulating its compound feed in the future.
A nutritionally balanced feed formula must be prepared according to the nutritional requirements of the farmed fish and the nutritional value of the feed. When formulating, the energy requirement of the fish must first be met. Protein, fat and carbohydrates in feed are all energy-containing organic substances, so as long as these three nutrients are satisfied in fish feed, the energy value is generally easy to satisfy. The focus should be placed on the content and proportion of feed protein and amino acids, so that they meet the requirements of nutritional standards. In addition, the crude fibre content in the feed should be controlled within the lowest range, so as to avoid a decline in the digestibility of other nutrients and the total digestibility of the feed.
A variety of feed raw materials should be selected for combination, so as to achieve the balance of protein and amino acids as far as possible. Various feed raw materials each have their own strengths in nutritional value; when combined, they make up for each other's shortcomings, and generally have a higher nutritional value than a single feed. Additives should also be appropriately selected to improve the nutritional composition of the feed and enhance the fish-farming effect of the feed.
The digestibility of each nutrient component of the feed raw materials and the palatability of the feed must be considered. Attention should be paid to selecting suitable feed according to the characteristics of the digestive physiology, feeding habits and preferences of different fish.
When designing compound feed and screening feed formulas, the greatest economic benefit should be sought, and consideration should be given both to the sources of raw materials and to convenience for storage, transport and use.
Examples of compound feed formulas for freshwater pomfret
Although people have not yet carried out in-depth and detailed research on the nutritional requirements of freshwater pomfret, it is currently at the experimental stage. However, because freshwater pomfret has omnivorous feeding habits and is not strongly selective about feed, various units have selected a variety of feed formulas for production practice and all have obtained relatively good fish-farming results. Several formulas are introduced below.
Several formulas of compound feed for freshwater pomfret
Zhang Zhongying et al. (1991) of the Yangtze River Fisheries Research Institute: for broodstock or fingerlings: fish meal 10%, soybean cake 25%, rapeseed cake and sesame cake 25%, rice bran 10%, wheat bran 10%, mixed feed (for pigs, containing about 13% crude protein) 18%, mixed salt mainly of calcium hydrogen phosphate 2%, plus 5% leftover flour as a binder. Crude protein content about 30-33%. For market-size fish: fish meal 5%, soybean cake 20%, rapeseed cake and sesame cake 30%, rice bran 15%, wheat bran 8%, mixed feed (same as above) 20%, mixed salt mainly of calcium hydrogen phosphate 2%, plus 5% leftover flour as a binder. Crude protein content about 25%.
Li Tianlai et al. (1989) of the Fujian Provincial Freshwater Fisheries Research Institute: for market-size fish: fish meal 15%, soybean cake 20%, peanut cake 20%, corn flour 25%, wheat bran 20%; after mixing, add 10 g of mixed inorganic salts and 200 g of table salt per 100 kg of feed. Crude protein 29.5%, feed coefficient 2.96.
Huang Erchun et al. (1994) of the Hubei Provincial Fisheries Research Institute; Hao Yanzhou et al. (1994) of the Shandong Provincial Fisheries School: for market-size fish: fish meal 15%, soybean cake 25%, fine wheat bran 50%, corn flour 8%, plus compound vitamins, minerals and table salt 2%. Crude protein about 27-28%. For fingerlings: fish meal 5%, peanut cake 30%, wheat bran 26%, shrimp bran 10%, corn 8%, flour 3%, locust leaves 2%, bone meal 1%, shrimp bait 15%, plus 75 g of inorganic salts and 40 g of compound vitamins added per 100 kg of feed. For overwintering fingerlings before New Year's Day. For fingerlings: fish meal 5%, peanut cake 34%, wheat bran 40%, shrimp bran 10%, corn 8%, locust leaves 2%, bone meal 1%, with the same amounts of inorganic salts and compound vitamins added as above, plus 20 kg of fresh miscellaneous fish added per 95 kg of feed. For overwintering fingerlings after New Year's Day.
The above formulas have shown good results after use. In order to improve the utilisation rate of compound feed, part of the green feed such as green vegetables and melon rind can be fed intermittently while feeding compound feed, which is beneficial to the rapid growth of freshwater pomfret.
Broodstock and fingerlings of freshwater pomfret are suitable for compound feed with 30-33% crude protein, and market-size fish are suitable for compound feed with 25% crude protein. Because freshwater pomfret has broad feeding habits and does not have high requirements for crude protein level, various places can formulate cheap, efficient and practical formulas according to local feed raw materials and price conditions.
Feeding techniques for compound feed
In fish farming production, after the fingerlings and feed have been resolved, feeding techniques become particularly important. To achieve efficient use of fish feed and maximum economic benefit, not only must the feed formula be reasonable and the nutrition comprehensive, but to a greater extent it depends on correct and effective feeding techniques.
Freshwater pomfret is a fish that lives in the middle and lower layers, and generally its feeding activities take place in the middle and lower layers of the water body. Therefore, compound feed needs to be made into sinking pelleted feed to be suitable for freshwater pomfret to eat.
Feeding methods
There are two ways to feed freshwater pomfret: one is to set up feed platforms in the pond, generally one per mu, 2-3 can be set up for 5 mu, and 4-5 for 10 mu; each feeding platform has an area of about 3-5 sq m, and the feeding platform should be about 50 cm below the water surface; the second is the hand-scattering method. When the pond water temperature is 27-30°C, freshwater pomfret feeds vigorously, and using only feeding platforms produces an inconspicuous effect and is not easy to observe. At this time, a person stands on the bank and scatters by hand, so that the vast majority of the fish can feed; this feeding method and feeding effect are relatively good.
In cage farming, it is generally not appropriate to set up feeding platforms, and hand scattering is better. This is because freshwater pomfret in cages has very strong schooling behaviour, and group activity is intense, often stirring the bait on the feeding platform so that it falls into the water, sinks to the bottom and is lost, thus causing relatively large losses, and the feeding effect is also relatively poor.
Optimum feeding amount
The feeding amount for freshwater pomfret is affected by many conditions such as the farming method, feed type and water temperature. Generally speaking, the feeding amount in cage farming is larger than in pond farming, the feeding amount in high-temperature seasons is larger than in low-temperature seasons, and the feeding amount in intensive ponds is larger than in mixed-culture ponds.
Yu Laining et al. (1988) once conducted experiments in this regard indoors using aquarium tanks. When the experimental water temperature was 26.5+2.4°C, and the daily feeding amount was 10.2% of the body weight of the pomfret, the daily growth rate was 5.7%; and when the feeding amount dropped to 2.3% of the fish body weight, the growth rate fell to 2.08%. The experiment found that during the fingerling farming stage of freshwater pomfret, the growth rate and feeding rate are in a direct proportional relationship within a certain range. The growth rate rises with the increase in feeding.
However, the feeding rate is limited by the amount of food intake and cannot increase indefinitely. If the feeding amount exceeds the food intake of the fish, it will cause waste of bait and increase farming costs. According to observations, after the feeding rate exceeds 10-20%, freshwater pomfret cannot finish eating it all. Therefore, their research concluded that the feeding rate should be limited to below 10%; if the water temperature is relatively low, it can be appropriately lowered a little. Considering that in natural waters, freshwater pomfret also habitually feeds on other bait, they suggested that in pond farming, controlling the feeding rate at 5-7% will obtain very good results. According to farming experience and experimental results from various places, whether for overwintering cultivation or natural normal-temperature farming of freshwater pomfret, as long as the water temperature exceeds 16°C, a certain feeding amount must be maintained to meet the needs of feeding and growth of freshwater pomfret. Under different water temperatures, in intensive ponds where freshwater pomfret is the main species, the feeding rate can refer to Table 2.
Table 2. Reference table of feeding amount for freshwater pomfret mainly cultured in ponds. Water temperature (°C) Feeding rate (%)16-20 0.3-1.020-24 1.1-2.024-28 2.1-4.028-30 4.1-7.030-33 7.1-10.0
Feeding rate means the daily feeding amount as a percentage of fish body weight. The change in feeding rate varies depending on many conditions such as fish body condition, size, water temperature and feed quality, and the specific daily feeding amount should be flexibly controlled according to specific circumstances. While feeding pelleted feed, if green feed is appropriately supplemented, the feeding rate can be relatively reduced. In ponds dominated by the four major Chinese carps, pelleted feed can be fed less or not at all; if the mixed-culture amount of freshwater pomfret is relatively small, conventional farming methods for the four major Chinese carps can be followed, without additional feed feeding. Therefore, the specific feeding amount should depend on various circumstances.
When freshwater pomfret is farmed in cages, its feeding rate is larger than the feeding amount in pond farming, mainly because cages lack the supplement of natural bait. The feeding rate in cage farming is shown in Table 3.
Table 3. Feeding rate of freshwater pomfret in cage farming under different water temperatures. Size (g/fish) Water temperature (°C) Feeding rate (%)4-10 28-30 14.7-1110-20 30-31 11-9.120-60 31-31.7 9.1-7.060-100 31.5-28 6.8-4.5100-125 28-25 4.5-3.2125-165 25-21 3.2-1.4
Feeding frequency, time and speed
Feeding frequency is the number of feedings per day and their reasonable distribution after the daily feeding amount has been determined. Freshwater pomfret is a fish with a stomach; its feeding intensity is great, its digestive capacity is strong, and its growth speed is fast. Its number of feedings varies with different water temperatures and different farming methods. Generally, in main-culture ponds, when the water temperature is between 20°C and 26°C, it is appropriate to feed 2 times a day; when it is higher than 26°C, the number of feedings should be 3-4 times. Cage farming should be 5-7 times.
It is relatively easy to train freshwater pomfret to eat at fixed times and places. Feeding at fixed times can improve the utilisation rate of feed and enhance the feeding effect. The choice of feeding time mainly depends on the temperature of the water environment. When the water temperature is low, feed once a day, preferably at noon; when feeding 2 times a day, choosing 9 o'clock and 15 o'clock is relatively suitable; when feeding 3 times a day, 8 o'clock, 13 o'clock and 18 o'clock are better, with an interval of about 5 hours each time. When freshwater pomfret is farmed in cages, when the fish grow to 70-80 g in mid-August, the fish often bite through the inner layer of the cage. According to research by Hu Tingjian et al. (1992), after mid-August, a feeding platform needs to be set up in the cage, and an additional feeding of feed on the feeding platform in the evening can effectively prevent the occurrence of cage biting. It can be seen that feeding techniques are related to whether freshwater pomfret bites the cage.
Feeding speed refers to the duration of each feeding. For well-trained freshwater pomfret, no matter which feeding method is used, even if there is a feeding platform under the water, it will not do to pour all the feed in at once. The feed should be slowly and continuously put into the water for the fish to ingest at that time. Freshwater pomfret generally feeds as it sinks, reducing the time the feed is soaked in water and the loss of feed nutrients; especially in the latter half of each feeding, the speed should be slowed down even more, and each feeding should last 20-30 minutes.
Processing and preparation of feed
The purpose of feed processing and preparation is to improve the palatability of the feed, make the fish like to eat it or easily swallow it, increase the digestibility of the feed, improve its nutritional value, maintain the nutritional components of the feed so that it does not dissolve and lose quickly after entering the water, and make the feed convenient for transport, storage and use.
Processing of single-item feed
In pond farming of freshwater pomfret, when the stocking density is relatively small, as long as natural bait can play a considerable role, single-item feed can also be used. Various single-item feeds often need to be processed before being fed to fish.
(1) Processing of plant-based feed and animal-based feed
Various cake and meal feeds must first be crushed and soaked before being fed to fish, and when rearing fry they should be ground into a slurry for use. When feeding fingerlings, they should be ground into powder or paste, and a certain amount of binder added to make a dough before feeding. For starchy feeds such as sweet potato flour, corn flour, barley meal and native flour, in order to improve their digestibility and their stickiness as a binder, they should first be heat-treated to gelatinise the starch, and then fed.
Large pieces of animal-based feed such as meat and fish-processing scraps and fresh miscellaneous fish should first be chopped and minced, and then a certain amount of binder added to make a dough for feeding. Fresh animal-based feed generally should not be cooked; feeding it raw gives higher digestibility, and the nutritional components are more