By Aquafeeds or aquaculture feeds are what we feed our cultured aquatic animals like fish and crustaceans. The feeds can be farm-made supplemental feeds for semi-intensive culture (low stocking density) or industrially produced complete feeds for intensive culture (high stocking density).
By Dr. Rafael D. Guerrero III
For intensive aquaculture, nutritionally balanced diets are required for the cultured species. The use of such feeds can account for 60 to 70% of the operational costs. When not properly used, complete feeds can be costly and cause pollution of the environment.
We learned about the efficient and judicious use of aquafeeds from the Workshop on the Development of Improved On-Farm Feed Management Practice conducted by the United States Agency for International Development (USAID) in General Santos City recently. Dr. Albert G.J. Tacon, a world-renowned fish nutritionist and technical director of Aquatic Farms, was the main lecturer.
Five factors influence the performance of aquafeeds, says Dr. Tacon. These are feed formulation and nutrient content; feed processing and physical properties; feed transportation and storage method; on-farm feeding method and staffing and pond biota and culture environment.
The global aquaculture industry utilizes the biggest supply of fishmeal and fish oil in the manufacture of aquafeeds, Dr. Tacon said. More than 70% of the said feed ingredients are used for cultured carnivorous species like shrimp, marine fishes, and salmon.
With the decreasing supply of and rising costs for fishmeal, the ingredient can now be partly or wholly replaced in aquafeeds with plant-based sources such as soybean meal and synthetic essential amino acids (e.g., methionine and lysine).
Complete feeds should have balanced nutrients that satisfy the requirements of the cultured species at its various stages (i.e., fry, juvenile, adult). Feeds should also be palatable and well accepted by the species.
In processing, feeds in their various forms (i.e., mash, crumbles, pellets) should be water stable and have the proper size and texture. No antibiotics should be incorporated in the feeds, and only approved additives such as vitamin and mineral premixes should be included.
From the feed plant, bagged feeds should be transported in closed trucks and not exposed to the sun and rain. During storage in well-ventilated areas, the feed bags should be placed on wooden pallets (not on the floor), and not stacked too high. The feeds usually have a shelf life of up to 3 months.
For on-farm feeding, the feeds should only be given in the ponds when the water temperature and dissolved oxygen in the water are favorable for the cultured species. “Shrimp cannot digest or optimally use feed unless the dissolved oxygen in the water is more than 4 parts per million (4 milligrams per liter of water).
The best temperature range for maximum digestibility and benefit from the feed is 29 to 31 degrees Celsius,” Dr. Tacon said. The feeding frequency (number of feedings per day) can be from 2 to 4 times, depending on the stocking density. For shrimp, the use of feeding trays is a good method for monitoring feed consumption and growth of the species.
Natural microorganisms in the pond can provide additional food sources for the cultured species and help “purify” the water, according to Dr. Tacon. The pond bottom where anoxic organic matter can accumulate should be properly managed through bioremediation (use of probiotics) or scraped out and oxidized to prevent disease outbreaks. It is also ideal to keep water transparencies at 30 to 40 centimeters.
This appeared in Agriculture Monthly’s May 2015 issue.
