Nutrition, Feeds, and Feeding
Nutrient requirements and feeding characteristics of channel catfish have been extensively researched. This research has provided the basis for the formulation of efficient, economical diets and for the development of feeding strategies - both of which have been instrumental in the success of the catfish industry.
Catfish farmers are able to feed a nutritionally complete diet that provides required levels of nutrients and energy in a readily digestible form. It is essential to provide a complete diet because natural food organisms only supply a small portion of the overall nutritional needs of catfish in intensively stocked ponds except during the early life stage. Forty nutrients have been identified as necessary for the normal growth and metabolic functions of channel catfish.
Protein is the most expensive nutrient of catfish feeds, so considerable work has been conducted over the last 20 years concerning the level of dietary protein and essential amino acids needed for cost-effective production of catfish. Data from these studies indicate that the dietary protein requirement for various life stages of catfish ranges from about 25 to 50 percent. Pond studies have shown that a protein level of 28 percent is adequate for food fish grow out when fish are fed to satiation daily.
Based on current knowledge, a digestible energy to digestible protein (DE/DP) ratio of 10-11 kcal/gram is optimal for growth of catfish raised from advanced fingerlings to market size. Ratios above this range may lead to increased fat deposition and reduced processed yield, and if the ratio is too low, that means some of the more expensive protein is used for energy which is not economical.
Catfish feeds contain grain and grain by-products that are rich in starch. In addition to providing an inexpensive energy source, starch helps bind feed ingredients together and increases expansion of extruded feeds so that the feed pellets are water stable and float in the water. A typical catfish feed contains 25 percent or more of digestible carbohydrates.
Fat is a concentrated source of energy and it can spare protein being used for energy. However, too much dietary fat will produce fatty fish which is undesirable for the consumer. Fat levels in commercial catfish feeds rarely exceed 5-6 percent. About 3-4 percent of the fat is inherent in the feed ingredients, with the remaining 1-2 percent being sprayed onto the finished pellets mainly to reduce feed dust or “fines,” but also to supply some energy and essential fatty acids. Both vegetable and animal oils/fats can be used for pellet coating, but animal fats (such as menhaden fish oil, catfish oil, and poultry fat or mixture) are typically used.
Catfish feeds are generally supplemented with a vitamin premix to meet dietary requirements and to compensate for losses due to feed manufacture and storage. Catfish feeds are also supplemented with phosphorus and a trace mineral premix to meet mineral requirements. Phosphorus supplements can be replaced by microbial phytase, an enzyme that can effectively release the bond-form of phosphorus in plant feedstuffs making it available to the fish.
Catfish feeds are mainly plant-based, though feeds for fry and small fingerlings contain some fish meal and other animal proteins. Major ingredients used in catfish feeds generally include soybean meal, cottonseed meal, corn and by-products, and wheat by-products.
There are various types of catfish feeds. The type being used at any particular time is a function of life stage and size of fish being fed, whether the fish are fed during the growing season or winter, and if an antibiotic is incorporated.
Catfish fry in hatcheries are fed finely ground meal- or flour-type feeds containing 45-50 percent protein. Once the fry are stocked in nursery ponds, they are typically fed a meal-type feed containing about 40 percent protein. Some producers feed fry with ”fines” from 28 or 32 percent protein feeds for food fish grow out until they reach 1-2 inches in length. During this stage, catfish fry can obtain most of their nutrients from natural foods such as large zooplankton, small insects, and insect larvae, if the ponds are properly fertilized.
Larger fingerlings are fed small floating pellets (1/8 inch diameter) containing 35 percent protein. Advanced fingerlings (5-6 inches) and food fish are generally fed a floating feed of approximately 5/32 - 3/16 inch in diameter containing 28-32 percent protein. Some producers switch to a slow-sinking feed during the winter.
Antibiotics are administered to catfish through incorporation in feeds (medicated feeds). Three antibiotics (Terramycin®, Romet®, and Aquaflor®) have been approved by FDA to treat bacterial infections in catfish.
Feed is the largest cost in catfish production, accounting for more than 50 percent of total variable costs, so how fish are fed directly affects profitability of catfish farming. Despite considerable research, feeding catfish is far from an exact science. It is a highly subjective process that differs among catfish farmers. The variation in feeding practices is a product of several factors such as cropping system, fish size, ability to manage water quality, experience of feeding personnel, and difficulty in estimating fish inventory.
In general, fish should be fed once a day with as much feed as they will consume without adversely affecting water quality. However, depending on water quality and health status of the fish, it may be advisable to restrict the daily feed allowance or to feed less often. Long-term feed allowance should not exceed 100-120 pounds for traditional ponds, and about 300 pounds per acre per day for split ponds and intensively-aerated ponds.
Most catfish producers feed once a day, 7 days a week during the warmer months. Research has shown feeding twice a day improves growth of fingerlings, but there is no benefit by feeding twice a day for food fish grow out.
Feed is typically blown onto the surface of the water using mechanical feeders. Feeds should be scattered over as wide an area as possible to provide equal feeding opportunities for as many fish as possible. Feeding with prevailing winds allows the feed to float across the pond and minimizes the amount of feed washing ashore. Overfeeding should be avoided since wasted feed affects water quality and increases production costs.
A Brief Overview of Catfish Nutrition
Catfish Protein Nutrition: Revised
Composition and Formulation of Channel Catfish Feeds
Comparative Quality of Foodstuffs for Catfish Feeds
Feed Conversion Ratio for Pond-Raised Catfish
Phytase Studies for Channel Catfish
Summary of Nutrition and Feeding Studies for Pond-Raised Hybrid Catfish
Feed Ingredients and Feeds for Channel Catfish
Feeding Catfish in Commercial Ponds