MANAGEMENT FOR ORNAMENTAL FISH PRODUCTION
Introduction
Most fish farmers and ornamental fish hobbyists buy the bulk of their feed from commercial manufacturers. However, small quantities of specialized feeds are often needed for experimental purposes, feeding difficult-to maintain aquarium fishes, larval or small juvenile fishes, and brood fish conditioning, or administering medication to sick fish. In particular, small ornamental fish farms with an assortment of fish require small amounts of various diets with particular ingredients. It is not cost effective for commercial manufacturers to produce very small quantities of specialized feeds.
Nutrition and Feed stuffs
Nutrients essential to fish are the same as those required by most other animals. These include water, proteins (amino acids), lipids (fats, oils, and fatty acids), carbohydrates (sugars, starch), vitamins and minerals. In addition, pigments (carotenoids) are commonly added to the diet of salmon and ornamental “aquarium” fishes to enhance their flesh and skin coloration, respectively. Find out the food and feeding habit/habitat of the fish to be cultured before fulfilling the nutritional requirements of different ornamental fish species, prior knowledge regarding food and feeding habits need to be collected. An herbivorous fish (plant source) will differ from carnivorous fish (animal source) in terms of its favorite food. Likewise, the feed of the fish feeding at the surface will be different from the fish living at the bottom. For example, protein requirements for different ornamental fish species vary with respect to feeding behavior and they can be supplied through varied sources as described below:
a. Herbivorous and omnivorous juveniles/grower and brood stock: 30-40 % (soybean meal, mustard meal, groundnut meal, wheat / maize gluten)
b. Carnivorous (e.g. cichlids): Above 45 % (Fish meal, squid meal, shrimp meal, clam meat)
c. Larval stages (most of the species): Above 50 % (natural/live food)
d. Maintenance feeds: 25-30 % (mixture of plant and animal based feed ingredients)
A feed is selected based on feeding habitat of the fish, food & feeding habits and habitat/niche of fish for maximum feed consumption and minimum wastage.
Example:
a. Surface feeders: Dry mash/meal
b. Column feeders: Mixture of dry/moist feed
c. Bottom feeders: Moist / wet / paste feed
The information on the nutritional requirements of ornamental fish are also collected for feed preparation
The nutritional requirement of ornamental fish varies with fish species, size, growth stages and feeding habits. It can be fulfilled by using different feed ingredients. In general, ornamental fish require 30-45 % protein, 4-9 % lipids and 30-50 % of carbohydrates in their regular diet but it vary with respect to development stage as given in Table-1.
In addition to major nutrients, binding agents (starch, agar, gelatin, etc.) and preservatives (antimicrobials and antioxidants) can also be added to improve the quality and shelf life of feed. Although, commercially available feeds for ornamental fish are fortified with carotenoids, but in case of farm made feeds, carotenoid supplementation is essential for enhancing color in ornamental fish, especially when reared under indoor conditions.
Selection of right fish feed ingredients for feed formulation
It is very important to identify locally available suitable feed ingredients which are capable of fulfilling the nutritional requirements of species of interest with respect to nutritive value, digestibility and nutrient availability. In addition to availability of quality feed ingredients, cost is another important factor which needs to be taken care of in feed formulation.
Proteins and Amino Acids
Fish meal, soybean meal, fish hydrosylate, skim milk powder, legumes, and wheat gluten are excellent sources of protein. Additionally, the building blocks of proteins (free amino acids) such as lysine and methionine are commercially available to supplement the diet.
Utilizing raw fish as a main ingredient in fish feeds has long been recognized to be harmful to the health and growth of fish due primarily to the presence of the anti-nutrient, thiaminase. Thiaminase, an enzyme that destroys thiamine (vitamin B-1), one of the essential water-soluble vitamins, is mostly found in freshwater fish and is destroyed by heat (i.e., cooking). Other concerns related to using raw fish in diets include the spread of infectious diseases such as mycobacterium and botulism. In preparing diets, preferential use of marine fish is suggested to minimize thiaminase activity, and raw fish could be steamed or poached.
Lipids: Oils from marine fish, such as menhaden, and vegetable oils from canola, sunflower, and linseed, are common sources of lipids in fish feeds.
Carbohydrates: Cooked carbohydrates, from flours of corn, wheat or other “breakfast” cereals, are relatively inexpensive sources of energy that may spare protein (which is more expensive) from being used as an energy source.
Vitamins and Minerals: The variety and amount of vitamins and minerals are so complex that they are usually prepared synthetically and are available commercially as a balanced and pre-measured mixture known as a vitamin or mineral premix. This premix is added to the diet in generous amounts to ensure that adequate levels of vitamins and minerals are supplied to meet dietary requirements.
Pigments: A variety of natural and synthetic pigments or carotenoids are available to enhance coloration in the flesh of salmon fish and the skin of freshwater and marine ornamental fish. The pigments most frequently used supply the colors red and yellow. The synthetically produced pigment, Astaxanthin (obtained from companies such as Cyanotech and F. Hoffmann-La Roche Ltd.), is the most commonly used additive (100–400 mg/kg). Cyanobacteria (blue-green algae such as Spirulina), dried shrimp meal, shrimp and palm oils, and extracts from marigold, red peppers and Phaffia yeast are excellent natural sources of pigments.
Binding Agents: Another important ingredient in fish diets is a binding agent to provide stability to the pellet and reduce leaching of nutrients into the water. Beef heart has traditionally been used both as a source of protein and as an effective binder in farm-made feeds. Carbohydrates (starch, cellulose, pectin) and various other polysaccharides, such as extracts or derivatives from animals (gelatin), plants (gum arabic, locust bean), and seaweeds (agar, carageenin, and other alginates) are also popular binding agents.
Preservatives: Preservatives, such as antimicrobials and antioxidants, are often added to extend the shelf-life of fish diets and reduce the rancidity of the fats. Vitamin E is an effective, but expensive, antioxidant that can be used in laboratory prepared formulations. Commonly available commercial antioxidants are Butylated Hydroxy Anisole (BHA), or Butylated Hydroxy Toluene (BHT), and Ethoxyquin. BHA and BHT are added at 0.005% of dry weight of the diet or no more than 0.02% of the fat content in the diet, while ethoxyquin is added at 150 mg/kg of the diet. Sodium and potassium salts of propionic, benzoic or sorbic acids, are commonly available antimicrobials added at less than 0.1% in the manufacture of fish feeds.
0 Comments