Thursday, July 18, 2024
Fishery

Nutritional Requirements of Fishes for Optimum Performance

Fish like any other livestocks especially farmed for commercial purpose will need food in order to sustain itself and to carry out other metabolic activities such as growth, respiration, reproduction and other life processes.

The nutritional requirements for meeting up with such demands are those that will enhance tissue build-ups, chemical synthesis and energy provision among others.

Therefore, a properly formulated, prepared feeds must have a well-balanced energy to protein ratio. The following nutrient sources are therefore a must part of fish diet in ensuring good returns to the fish farmer.

Nutritional Requirements of Fishes for Optimum Performance

1. Protein

Fishmeal is added to fish and poultry diets as a source of highly digestible, “high quality”, animal protein. Animals synthesize proteins from 22 amino acids. However, animals cannot synthesize all 22 of these amino acids. Amino acids which can not be synthesized by animals, and therefore must be supplied in the diet, are classified as essential.

Those that can be synthesised by the animal are termed nonessential. Of these, a few cannot be synthesised at a rate fast enough for maximum growth and, therefore, are considered dietary essentials in fish feed.

The nutritional value of any protein is directly related to the amino acid composition of that protein. A protein that does not contain the proper amount of required (essential) amino acids would be an imbalanced protein and would have a lower nutritional value to the bird.

Proteins of cereal grains and most other plant protein concentrates fail to supply the complete amino acid needs of fish, due to a shortage of methionine and/ or lysine.

Soybean meal, which is widely used in poultry diets, is a good source of lysine and tryptophan, but it is low in the sulfur-containing amino acids methionine and cysteine. Fishmeal is an excellent source of all of these amino acids. A well-balanced protein, such as that found in fishmeal, is considered to be of high nutritional value for the fish.

Feedstuffs are combined to meet the bird’s need for the most limiting amino acids, as well as other nutrients and energy. This can sometimes result in a higher than required protein content of the diet due to the presence of other amino acids in excess.

The excess amino acids are not used for the function of protein synthesis. Instead they are deaminated and their carbon skeletons used as an energy source or stored for use as an energy source at a later time. This method of furnishing excess amino acids is very expensive and is an inefficient overall use of the dietary protein.

Using synthetic amino acids, diets can be formulated which meet the bird’s amino acid requirements but with a reduced total protein content. This provides the appropriate levels of essential amino acids while avoiding large excesses of other amino acids.

Fishmeal contains an excellent quantity and profile of amino acids which can also offset the deficiencies of certain limiting amino acids in cereal grains. The protein in fishmeal is an excellent source of the essential amino acids lysine, methionine and tryptophan. It is because of this that fishmeal is often used as the supplement of choice for vegetable protein, especially soybean meal.

2. Minerals (Ash)

Minerals are inorganic elements necessary in the diet for normal body functions. They can be divided into two groups (macro-minerals and micro-minerals) based on the quantity required in the diet and amount present in fish. Common macro-minerals are sodium, potassium chloride
and phosphorus while examples of micro-minerals include copper, chromium, iodine, zinc and selenium.

These minerals regulate osmotic balance in fish and aid in bone formation and integrity. Fishmeal is an excellent source of calcium and phosphorus for fish. The ash (mineral) content of fishmeal can range from 10 to 25%.

The higher ash content is usually an indication of a higher calcium and phosphorus level. The calcium and phosphorus are in a highly available form, unlike some of the calcium and phosphorus in plant proteins.

One of the only minerals in fishmeal that is not readily available to poultry is the trace mineral selenium. The selenium in fishmeal exists in the form of seleno proteins which are not considered to provide readily available selenium to the fish. Also fish can absorb many minerals directly from the water through their gills and skin, allowing them to compensate to some extent for mineral deficiencies in their diet.

3. Energy

The energy content of fishmeal is directly related to the percentage of protein and oil (fat) in the meal. Usually the metabolisable energy (ME) value of fishmeal ranges from 2500 to 3200 Kcal ME/kg. The quantity of oil present in fishmeal depends on the species, feeding habits of the fish, and the method of processing.

The use of antioxidants in the preservation of fishmeal is essential in order to ensure a higher ME value for the fish and poultry. Without stabilizing the fishmeal with antioxidants, the ME of the meal may be reduced by as much as 20%. Prior to the development and use of
antioxidants by the fishmeal industry, it was common practice to turn piles of processed meal in order to dissipate the heat arising from the oxidative process.

Occasionally, these piles of stored meal or during transit, fishmeal would combust spontaneously and cause fires and decrease the nutritive value. It was common several years ago to hear of ships sinking due to fires caused by spontaneous combustion of fishmeal. Today, transatlantic transported fishmeal, by law, must contain an effective antioxidant.

4. Fatty Acids

The oil present in stabilised meal has a relatively low concentration of linoleic acid, an essential fatty acid for poultry. However, the oil is an excellent source of the essential fatty acid, linolenic.

The fatty acids present in the oil in fishmeal can contribute to the requirement of poultry for essential fatty acids. Supplementing low levels of fishmeal in broiler and laying hen diets has been shown to increase the omega-3-fatty acid content of broiler meat and eggs.

Current knowledge in the area of cardiovascular disease indicates that the presence of the omega-3-fatty acids in the human diet is related to a lower incidence of heart attack.

5. Vitamins

Vitamins are organic compounds necessary in the diet for normal fish growth and health. They often are not synthesized by fish, and must be supplied in the diet. The two groups of vitamins are water-soluble and fat soluble.

Water-soluble vitamins include: the B vitamins, choline, inositol, folic acid, pantothenic acid, biotin and ascorbic acid (vitamin C). Of these vitamin C probably is the most important because it is a powerful antioxidant and helps the immune system in fish.

The fat-soluble vitamins include A vitamins, retinols, the D vitamins, chole calciferols, E vitamins, tocopherols (antioxidants) and K vitamins such as menadione. Of these, vitamin E receives the most attention for its important role as an antioxidant.

Deficiency of each vitamin has certain specific symptoms, but reduced growth is the most common symptom of any vitamin deficiency. Scoliosis and dark coloration may result from deficiencies of ascorbic acid and folic acid vitamins respectively.

Read Also:  Fish Nutrition, Feeds and Feeding

Read Also: Products That Can Be Derived From Metabolic wastes

Agric4Profits

Benadine Nonye is an agricultural consultant and a writer with several years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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