Annex Q: Extruded Diets Produced by Dr. Wimol

Annex R: Penkhar Nasuwan's Soybean Meal Diets for Clarias

Annex S: Siriporn Rajchapakdee's Carbohydrate Diets for Clarias

Annex T: Quantitative Recovery of Nitrogen during Kjeldahl Nitrogen Analysis

• Determination of size of ammonium sulfate sample needed for recovery analysis.

Nitrogen has an Atomic Weight of 14.01 g/mol.
The amount of nitrogen in ammonium sulfate is 28.02/132.14 = .212 (21.2%)

A 0.5 gram sample of Fish Meal containing 10.84 % N has 0.054 g N
A 0.2 gram sample of ammonium sulfate containing 21.2% N has 0.042g N

Therefore, a 0.2 gram sample of ammonium sulfate will use about the same amount of acid as 0.5 g of fish meal when titrated.

Annex U: Notes for Lecture on Proximate Analysis and Nutrient Analysis

PROXIMATE ANALYSIS

1. WATER—

   We need to know the water content of feeds because if there is too much water remaining in a feed, spoilage may occur. Yet drying using machinery is expensive. It is important to dry feeds to the degree that they will not spoil, but not so much that we are wasting energy. Some fish prefer to eat feeds which are not too dry and hard, and for this reason, our feeds may need to have a specific percentage of water

2. CRUDE PROTEIN—

   Crude protein is usually determined by Kjeldahl analysis, which measures nitrogen and not protein. The amount of nitrogen, expressed as a percentage, is usually multiplied by a factor such as 6.25 to obtain an estimate of crude protein. The Kjeldahl method will measure essential amino acids, non essential amino acids, free amino acids, amines and nucleic acids. Because it is not specific, it will also measure two non-protein sources of nitrogen which must be considered. If shark meat is being analyzed, it has a very high concentration of urea which will give a Kjeldahl measurement which is too high. The amount of urea must be measured and subtracted from the Kjeldahl measurement. Chitin, which is a nitrogen-containing material very much like cellulose and is found in the carapace of insects and crustaceans, can also give high Kjeldahl measurements. When analyzing crustaceans, the shell should be separated from the meat, and analyzed separately to determine the percentage of nitrogen. The amount of nitrogen in the chitin can be subtracted from the total Kjeldahl nitrogen of whole animals.

3. ETHER EXTRACT : LIPIDS—

   This is called ether extract because ether is the organic solvent which is usually used to extract lipids, although a number of other solvents, for example 2:1 chloroform:methanol, are commonly used. Depending on the solvent used, the ether extract can contain triglycerides, free fatty acids, phospholipids, sterols, fat soluble vitamins and other lipids such as waxes and sphingomyelins.

4. CRUDE FIBER—

   Crude fiber is determined by washing a lipid-free feed or feed ingredient with weak acid and weak basic solutions, which leaves only insoluble polysaccharides such as cellulose, hemicellulose, pectin and lignin. Chitin, because of its structural resemblance to cellulose, is also retained in crude fiber analysis.

5. ASH—

   Ashing is done by heating a feed in a furnace at 550–600°C until all organic material has been burned away. Ash contains essential minerals, non-essential minerals and toxic elements such as heavy metals.

6. NITROGEN-FREE EXTRACT : CARBOHYDRATES—

   The NFE component contains simple sugars (monosaccharides and disaccharides), complex sugars (polysaccharides), soluble sugars (glucose and glycogen), and the water soluble vitamins.

   NFE is usually calculated by subtracting all of the other components from the total amount of the feed : NFE = 100% - % crude protein - % ether extract - % crude fiber - % ash

7. ACCURACY OF PROXIMATE ANALYSIS—

   Crude protein : value±10% of the value
   Ether extract : value±8% of the value
   Ash : value±4–5 % of the value
   Fiber : value±10–15 % of the value
   NFE : value±8 % of the value

   Report proximate analysis values to 2 decimals, and means derived from multiple values to 1 decimal.

NUTRIENT ANALYSIS

Nutrient analysis is more than proximate analysis, more than just the determination of the amounts of protein, lipid, and carbohydrates in a feed. The concern is about the quantity and quality of nutrients (the balance of amino acids and minerals, ratios of fatty acids, etc.), as well as digestibility of nutrients and their utilization. Nutrient analysis also deals with “antinutrients” — substances present in feedstuffs and feeds which reduce the assimilation, utilization or effectiveness of nutrients, or cause disease due to their presence. Finally, analysis for the presence of contamination or adulteration is also part of nutrient analysis.

1. PROTEIN QUALITY

   Digestibility Determinations (total protein, amino acids, essential amino acid balance).
   Protein Dispersibility.
   Available lysine.
   Protein Efficiency Ratio, Net Protein Utilization.

2. LIPID QUALITY

   Balance between essential/non-essential lipids.
   Oxidative Rancidity:
        Peroxide Value;
        Thiobarbituric Acid (TBA);
        Iodine Value;
        Ratios between saturated and unsaturated fatty acids;
        The presence of preservatives;
        Tocopherols (Vitamin E).

3. ASH QUALITY

   Salt (sodium chloride in marine fish meals)
   Calcium: Phosphorus ratios

4. CARBOHYDRATE QUALITY

   The amount of digestable starch and sugars, and carbohydrate digestibility.

5. AVAILABILITY OF ENERGY

   Calorimetry of feedstuffs and feeds can be used to determine gross energy values.
   Calorimetry of fecal materials allows the determination of digestable energy (DE) coefficients.

ANTI-NUTRIENT ANALYSIS

Many anti-nutrients are found in the oilseed meals, the residue left after extraction of oil from a variety of seeds, and beans.

1. Soybeans and other Legumes —
   Phytic acid — interferes with mineral uptake and utilization, especially calcium iron and zinc. 70% of the phosphorus in soybeans is found in phytate. Phytate can be removed chemically, but this is expensive. It is not destroyed by cooking, but soaking will remove soluble phytates. Additional zinc is often added to high-phytate feeds.

   Trypsin Inhibitor — interferes with the tryptic enzymes in the small intestine, and impairs protein digestion. Proper cooking of feedstuffs will usually destroy trypsin inhibitor.

2. Cottonseed Meal and Peanut Meal —
   Molds and Aflatoxins — the presence of molds, particularly mutant strains of Aspergillum flavus which produce highly carcinogenic aflatoxins, can be a problem with peanut and cottonseed meals when peanuts or cottonseeds are improperly harvested or stored before oil extraction. 0.5 ppb aflatoxin fed to rainbow trout only once was enough to induce, within 6 months, liver tumors in 50% of the fish which were fed. Some forms of aflatoxins can be deactivated by heat, but there are forms which are highly resistant to denaturation. Use of feedstuffs and feeds containing molds should be avoided.

3. Rapeseed Meal —
   Glucosinolates which inhibit thyroid function, are present in most seeds of plants in the mustard family (Brassica spp.). This does not prohibit their use, but limits the amount which can be used safely in feeds without noticeable effect.

CONTAMINATION AND ADULTERATION

1. Contaminants — can be anything in feedstuffs and feeds which is not naturally present, but is acquired through cultivation, harvesting and processing methods of plant materials, or though the bioaccumulation in living animals. Common contaminants are fertilizer and pesticide residues, heavy metals, petroleum products, lipid soluble organic compounds such as PCB's and dioxins. Most chlorinated hydrocarbons which are found in fish feeds come from fish meals, but ingredients such as cottonseed meal can have residues of pesticides used to control insects which destroy cotton plants.

2. Adulterants — The best protection against adulteration, which is the deliberate addition of contaminants to feeds and feedstuffs, is a good quality control program. An adulteration control program can be established with a microscope and a few simple chemical tests. If a supplier knows that the adulteration of fish meal with rubber seed meal will be discovered, and that he will not be paid a good price, or that the feedstuff will be refused, he will not try to sell it to you. If a good quality fish meal is adulterated with a poor quality fish meal, the poor quality fish meal will have a high free nitrogen content and perhaps also a higher ash content than normal. Establish a quality control program for all incoming and outgoing products. It is a sensible way to protect a feed producer from being cheated, and also gives a producer information which can be used to handle complaints from feed buyers.

Annex V: Notes for Lecture on Raw Materials for Feed Ingredients

There are many raw materials which can be used in formulations which will produce good growth of fish and crustaceans. Generally, feedstuffs are chosen because they contribute one or more nutrients at a better price than other materials can, or because they provide better quality nutrients. There are four main types of nutrients

1. CARBOHYDRATE SOURCES—

   Corn; wheat; rice; cassava; tapioca.
   Can be used for nutrients as well as for increasing pellet binding and water stability. Many starchy products require some cooking to increase the digestibility and utilization of the carbohydrate.

2. PROTEIN SOURCES—

   PROTEINS FROM ANIMAL SOURCES—

   Meat and Bone Meal - made from butcher shop wastes and dead and fallen animals.
   Poultry Byproduct Meal - made from body parts of poultry which are removed during processing.
   Blood Meal - blood obtained from slaughterhouses which has been cooked and ground. Depending on cooking method, digestibility may be poor.
   Fish Byproduct Meals
        viscera meal - amino acids probably not balanced.
        white fish meal - high ash.
        tuna meal - has been cooked twice if byproduct of tuna canning. Protein availability may be low, and lipids are deteriorated.
   Fish Meals - anchovy, herring, menhaden, smelt.
   Fish Silage - fish or fish wastes digested with acid.
   Condensed Fish Solubles - Dehydrated liquids from fish processing.
   Trash Fish - Use of trash fish, while cheap and readily available to small-scale fish farmers, should be discouraged. The main problem with trash fish is that it has a significant polluting effect,—it increases nitrogen loading and increased biological oxygen demand (BOD). Trash fish can contain an enzyme call thiaminase, which can destroy thiamin in wet fish feeds. Heating destroys thiaminase. All raw fish should be cooked to pasteurize and sterilize it. This not only increases the shelf life of any feeds made with it, it also decreases the chance of passing infective diseases from one fish to another through the feed. Generally, diseases which affect marine fish do not have little if any effect on fresh water fish, and vice versa, so there is less possibility of a disease problem if marine products are fed to fresh water fish, or fresh water fish are fed to marine fish.

   PROTEINS FROM PLANT SOURCES—

   The main concern with plant-source proteins is the relatively low levels of several amino acids, primarily lysine and methionine, compared with animal source proteins Some major sources of plant proteins:

   Oilseed Meals - byproduct of the vegetable oil extraction industry.

   Full-fat Oilseed Meals - increasing popular feed ingredient where farmers grow both oilseeds and feed livestock or fish on their farms.

   Corn Gluten Meal - byproduct of the corn oil processing industry.

   Brewer's Grains - byproduct of beer making. May decrease binding of feed mixtures in pelleting.

   Distiller's Dried Grains - byproduct of liquor industry.

   There are a number of high protein plants which have been investigated, but more work needs to be done in Asia:
        Mung Bean Meal;
        Peanut Meal;
        Leucaena;
        Winged Bean plants and seeds;
        Algae.

3. LIPID SOURCES—

   Fish Oils - high in long chain fatty acids.
   Animal Fats - high in saturated fats; can be used for cheap energy.
   Vegetable Oils - often contain high levels of tocopherols.

4. VITAMIN AND MINERAL SOURCES—

   Generally, feed manufacturers assume that all of the unstable vitamins will have been destroyed during processing, and will add vitamin mixes which contain all of the vitamins known to be required by the animals at levels that will meet or exceed the known requirements. Feeds which contain feedstuffs with high levels of phytate, or cereal grains that lack essential elements such as zinc or selenium, will be used because feed manufacturers often include mineral mixes in feeds. Supplementation of all minerals is not essential except in cases where the water is very pure and does not contain minerals. Mineral and vitamin mixes can often be left out of feeds which are used for semi-intensive fish farming, because the fish obtain enough of the substances from the natural feeds in the aquaculture system.

5. ATTRACTANTS AND FEED STIMULANTS—

   Anything with high free amino acids will make a good attractant:

   Squid viscera; shrimp and crab process waste; fish silage; fish solubles, distiller's and brewer's grains.

   Synthetic compounds which are used are often based on the amino acid betaine, which is derived from sugar beet processing.

Annex W: Notes for Lecture on Feed Production

1. CLEANING— Sieves and Magnets

Feed mill equipment is expensive to purchase and expensive to repair. To protect this equipment, it is necessary to make sure that all ingredients coming into the feed mill are cleaned. First, try to purchase clean materials. Second, install good screens and magnets at the point of raw materials entry into the mill to remove field debris and any metal parts from harvesting and transportation equipment which may have fallen into the raw materials. Third, install several magnets in the feed production line to catch any metal parts which may come from processing equipment in the mill itself. A bolt may come out of a bucket elevator assembly, and destroy an expensive extruder. Do not underestimate the importance of magnets! Put one ahead of any expensive piece of equipment, such as pellet mills and extruders, which can be damaged.

2. GRINDING—

With fish feeds, fine grinding is usually always necessary. A uniform small particle size (always less than 250μ, and often below 100μ for feeds for small fish) helps to maximize nutrient digestibility, is needed to produce high quality extrusion feeds, and is particularly important in giving superior binding properties to shrimp feeds for better water stability. Grinding is expensive, and unfortunately, the finer the grind desired, the slower the output of the grinder will be. However, since grinding is so important in making good feeds, do not try to save money by increasing particle sizes above those recommended.

Sometimes grinding materials which contain high amounts of oil, such as fish meals, and full-fat soybean meals, can be a problem as they cake badly in grinders. Premixing oily materials with dry starchy materials such as rice or wheat flours will make grinding easier.

3. MIXING—

What happens when mixing is occurring is not well understood. Feeds are often undermixed. A fine grind feed containing 50 million particles should not be expected to mix adequately in the amount of time needed to properly mix a coarse grind feed containing 5 million particles. A ribbon mixer needs a minimum of 5 minutes to do an adequate job, and more time would be better. Any less time than that, and you cannot be sure that proper mixing has occurred. If a fish will eat only 6 pellets of feed today, can you be sure that each pellet is balanced for nutrients and contains all of the nutrients it will need to grow? Grinding feed ingredients as fine as possible, and mixing them well is the only way to ensure that feeds will be balanced for nutrients, and that a fish will obtain all the needed nutrients every day.

4. PELLETING—

The decision to make a certain kind of pellet must be based on knowledge of the animal's biology, physiology and behavior, and the nature of the culture system being used. For example, trying to feed mud crabs with pelleted shrimp feed will not work because mud crabs need to be able to pick up large pieces of feed in their claws to be able to eat. As another example, shrimp are nocturnal feeders, and yet many feeding regimes employed at shrimp farms are only during daylight hours. A highly water stable diet fed at dusk which can sit uneaten on the bottom without appreciable nutrient loss can extend the actual feeding time well beyond the quitting time of a shrimp farm's employees.

Moist Feeds — made with a meat grinder from fish process wastes or trash fish and combinations of dry materials, can be very good, high nutrient quality feeds, if made properly. These feeds should be used quickly, as they can spoil easily.

Dry Compressed Pelleted Feeds— were the standard feeds around the world for many years. They have the advantage of being easy to handle and store, and do not cost as much as extruded feeds. Temperature obtained during dry compressed pelleting are usually not as high as temperatures achieved with extrusion systems. This is good in the sense that heat-sensitive nutrients are not as likely to be damaged or destroyed as they would be in extrusion systems. On the other hand, dry compressed pelleting does not give the full cooking of carbohydrates attainable with extrusion systems, and this makes carbohydrate sources less digestible.

Dry compressed pellet machines make excellent sinking feeds, and with wise use of binding agents, can make feeds with good water stability. In many cases, as a way of saving money, dry compressed feeds can be fed in mixtures with extruded floating feeds, since dry compressed feeds do not cost as much to make as extruded feeds, and yet can deliver nutrients almost as well. Although there is a lot of interest in extruders right now, as our knowledge of feed technology increases, our ability to make economical, highly digestable feeds using compressed pellet machines should also expand.

Extruded Feeds — Most of the recent interest in feeds has been in the development of extruded feeds. Feeds which have ingredients such as soybean meal and cereal grains can be made more digestable, and the nutrients are therefore more available. In some cases, extruders are used just to prepare feed materials, such as dry extrusion of soybeans. Floating feeds are made using extruders. Highly water-stable sinking feeds can be made with extruders as well.

Basically, an extruder is a long barrel with a screw auger inside which is specially designed to subject feed mixtures to high heat and steam pressure. When feed exits the die at the end of the barrel, trapped steam blows off rapidly, the soft warm pellets expand, and a low density floating pellet is produced. Extruders are very versatile, and can make feeds with many different characteristics. The main problem with extruders is that they are expensive to buy and maintain, and the feed manufacturers pass this cost on to feed buyers.

Soft-dry Feeds— Another type of feed which can be made on extruders, soft-dry feeds are usually high in moisture (12–15%) and fat (15%). They usually contain a number of preservative agents to prevent spoilage. Soft-dry feeds can be used for fish that prefer to eat soft feeds, yet they do not need refrigeration like moist feeds.

5. DRYING—

Drying is essential to prevent spoilage in feeds, which can occur when moisture levels remain too high. Spoilage can be molding caused by fungi or fermentation by bacteria or yeasts. Generally, if the moisture content of a feed is less than 12%, spoilage will not occur. It is possible to dry feeds using air drying, sun drying or drying ovens. Using drying ovens can be expensive, and drying using air or sunlight is often practiced here in Asia. Air drying under shade is the preferable method, as sun drying exposes feeds to ultraviolet light which can cause oxidation of lipids in materials which contain a lot of marine oils, such as shrimp head meals, squid meals, and so on.

6. STORAGE—

Finally, a few comments about storage.

• Always refrigerate moist feeds unless they are going to be fed immediately.

• Refrigerate semi-moist feeds if they are going to be fed on a daily, or next-day basis. If semi-moist feeds are to be stored longer, either freezing or drying is preferable.

• Store dry feeds in a cool dry place. Do not freeze dry feeds as a means of increasing storage time. This is a very common practice, but it is done because people do not understand what can happen. In a dry feed, spoilage is prevented because the ability of spoilage organisms to get water is kept at a minimum, since the water is dispersed evenly at low levels throughout the pellet. However, if you freeze a dry feed, water crystallizes and collects together. When the feed thaws out, the collected water can lead to rapid microbial spoilage and the destruction of moisture-sensitive vitamins like vitamin C. Therefore, do not freeze dry feeds.

Annex X: Notes for Lecture on Feed Formulation

CHAPTER 15

FISH FEED FORMULATION

R. Hardy
University of Washington
Seattle, Washington

^FROM: 1980. Fish Feed Technology. ADCP/REP/80/11. FAO, Rome.

1. INTRODUCTION

Feed formulation is essentially applied nutrition. A number of terms and expressions are introduced that will be put to practical use as information is presented on the nature and qualities of various feedstuffs and the information presented on the nutrient requirements of fish. Precise understanding of these terms is essential to their correct application. One must recognize that some of these terms have a built-in error that cannot be escaped. This does not eliminate their usefulness in feed formulation. However, one must appreciate the fact that some are useful approximations of the values and not true values.

The terms that one needs to understand to formulate practical fish diets are: crude protein level; energy level, either expressed as metabolizable energy (ME) or as digestible energy (DE); specific amino acid levels; crude fibre level; and ash level. Since most complete practical fish diets are supplemented with a vitamin premix at levels in excess of the dietary requirement, this category of nutrients will be ignored temporarily. The potential problems occur when one fails to recognize that all of the above mentioned terms, except ME and DE, represent the quantity or level of a nutrient in the feed as determined by chemical tests on a specific sample of a feedstuff. These chemical tests generally correlate well enough with biological methods of feed evaluation (growth studies, tissue levels) to be very useful to feed formulators, but they are still chemical tests that are subject to experimental error during nutrient level determination. For example, the proximate composition of fish meals changes during the spawning season. Generally, the lipid levels increase before spawning and decrease after spawning. This will alter the percent of protein, ash, and carbohydrates in fish meal as the seasons change. Similarly, many plant feedstuffs vary in proximate composition with their stage of maturity at harvest, location grown, and other environmental conditions, such as the weather. Tabled values represent an average value that is usually close enough to the actual value to allow accurate feed formulation. However, one must be aware that assumptions are being made in order to recognize the potential sources of error that may exist.

Metabolizable energy and digestible energy values are obtained biologically and, thus, should accurately represent the true energy value of feedstuffs to fish. However, ME values may be obtained in different ways (faeces collection methods) and thus may be subject to experimental error. It has recently been reported that the digestibility of feed by rainbow trout was lower at 7°C than at 11°C or 15°C. At 11°C and 15°C body size (18.6 g, 207.1 g or 585.7 g) did not affect feed digestibility. The digestibility of carbohydrate and energy was slightly reduced by meal size in rainbow trout fed at 1.6 percent body weight. Protein and lipid digestibility was not reduced by meal size. Obvious differences exist between fish species in nutrient digestibility, especially in the carbohydrate fraction of feed. Herbivorous and, to a lesser extent, omnivorous fish have longer digestive tracts than do carnivorous fish and are able to obtain more digestible energy from carbohydrates. An awareness of these facts will prevent misuse of ME and DE values.

Each feedstuff in any diet formulation should be present for a specific reason; i.e., it is a good energy source, it is rich in a limiting amino acid, etc. In addition, each feedstuff in a particular diet formulation should be the least costly ingredient available for its particular function in the diet. This leads to another assumption in feed formulation; that is, any nutrient in a particular feedstuff, such as an amino acid, is just as valuable as the same nutrient in any other feedstuff. This allows feed formulators to interchange one feedstuff with another as cost and availability change. Thus, it is assumed that there is no “ideal formulation”, but rather an almost infinite number of possible feed formulations that met the nutritional needs of the fish equally well. While this assumption may not be entirely valid and some nutritional judgement must be employed in any feed formulation, it does seem to be valid in most cases. As with the previously mentioned assumption, an awareness of the potential pitfalls involved is necessary for the fish feed formulation so that allowances can be made in diet formulation and problems can be anticipated and avoided.

BALANCING CRUDE PROTEIN LEVEL

In most animal diets, protein is the most expensive portion and is usually the first nutrient that is computed in diet formulation. The energy level of the diet is then adjusted to the desired level by addition of high energy supplements; which are less extensive than protein supplements. The square method is an easy way to determine the proper dietary proportions of high and low protein feedstuffs to add to a feed to meet ie dietary requirement of the animal to be fed.

For example, suppose rice bran and soybean meal were available as feedstuffs to prepare a diet for carp that was 25 percent crude protein. A square is constructed and ie two feedstuffs are put on the two left corners along with the protein content of each. The desired protein level of the feed is placed in the middle of the square. Next, the protein level of the feed is subtracted from that of the feedstuffs, placing the answer in the opposite corner from the feedstuff. Ignore positive or negative signs.

To make the 27 percent crude protein in carp feed, we must mix 17/35.8 of rice bran with 18.8/35.8 soybean meal.

So to make 100 kg of this feed we must mix 47.5 kg of rich bran with 52.5 kg of soybean meal.

If more than two feedstuffs are used in a feed, they may be grouped into basal feeds (CP < 20 percent) and protein supplements (CP > 20 percent), averaged within each group, and plugged into the square method. For example, suppose shrimp meal and corn were also available for the carp feed mentioned above. The crude protein levels of the shrimp meal (52.7 percent) and of corn (10.2 percent) are averaged with soybean meal and rice bran, respectively.

Thus, to make 100 kg of this feed one would mix the following:

The square method is helpful to novice feed formulators because it can get them started in diet formulation without the need to resort to trial and error. The square method can also be used to calculate the proportion of feedstuffs to mix together to achieve a desired dietary energy level as well as a crude protein level. If one wanted to make a feed containing 2 500 kcal ME/kg using wheat middlings (1 663 kcal ME/kg) and anchovy fish meal (4 371 kcal, ME/kg) a square could be constructed as follows:

The square method cannot be used to simultaneously solve for both crude protein level and ME level.

3. STEPS IN FEED FORMULATION

The first step in diet formulation is balancing the crude protein and energy levels. This can be accomplished by trial and error, by the square method for either crude protein level or energy level and then adjusting, or by solving simultaneous equations. At first, it is helpful to use at least three feedstuffs during the initial balancing of protein and energy levels: one high in protein and high in ME, one low or intermediate in protein and high in ME, and one low or intermediate in both protein and ME. Once practice makes one more proficient at diet formulation any number of feedstuffs can be used. One must remember to reserve room in the formulation for any feed additive, such as a vitamin or mineral premix.

The second step in diet formulation is to check the levels of indispensable amino acids in the formulation to be sure the dietary levels meet the requirements of the animal to be fed. The requirements of fish for indispensable amino acids is expressed as the dietary level (as a percent of the diet) or as a percent of the dietary protein level. To convert an amino acid level from the percent of diet to percent of protein, divide the dietary level of each amino acid by the dietary protein level. It might be of interest to calculate the dietary levels of all of the indispensable amino acids, but it is not practical to do it all of the time. If the levels of arginine, lysine, methionine, and tryptophan meet the dietary requirements of the fish to be fed, the levels of the other six indispensable amino acids will most likely be above required levels. When using unconventional protein supplements, the levels of all ten indispensable amino acids should be checked.

If the diet formulation is low in any amino acid, a feedstuff that contains high levels of that amino acid must be added to the diet at the expense of another ingredient. Once the amino acid requirements are met, the dietary protein and energy levels must be rechecked to see if any substitution of ingredients has imbalanced the formulation.

A diet mixing sheet should be constructed to standardize diet formulation. A sample sheet is shown in Table 1. The amino acids listed are for illustration purposes only and may be changed to suit different circumstances.

In practical feed formulation, pellet quality and acceptability must be considered in addition to nutrient levels and cost. These considerations will vary from species to species and with the type of pellet being made, and are dealt with in other sections of this manual.

4. BEST-BUY TECHNIQUES

The price of the feedstuffs used in diet formulations must be considered to formulate a cost-efficient diet. Feedstuffs can be compared with one another on the basis cost per unit of protein, energy, or amino acid. For example, suppose one has wheat middlings and wheat millrun available for a fish diet, which feedstuff would be the least expensive source of energy?

Wheat millrun costs US $ 0.0858/kg, and contains about 1 200 kcal ME/kg.

Wheat middlings cost US $ 0.1883/kg and contain 1 663 kcal ME/kg.

Thus, the wheat millrun which has a lower ME value for fish is the better buy because it costs less per kcal.

To compare oat groats and wheat middlings on a cost per unit ME basis one would do the following:

Wheat middlings = US $ 0.001132/kcal, and

Oat groats cost US $ 0.2652/kg, and contain about 2 450 kcal ME/kg.

Oat groats, although costing more than wheat middlings, constitute a better buy on an energy basis.

The cost of protein is often the greatest part of the cost of a fish diet. Therefore, substantial savings can be made by using best-buy techniques to determine the least expensive protein supplement. To compare anchovy meal and herring meal, the following calculations are made:

Anchovy meal costs US $ 0.5357/kg, and contains 70.9 percent protein.

Herring meal costs US $ 0.4709/kg, and contains 76.7 percent protein.

On the basis of cost per unit protein, herring meal is less expensive as a dietary ingredient than is anchovy meal.

To compare feedstuffs on the basis of cost per unit of an amino acid, one can calculate the best buy in the same way as before.

For example, sesame oil cake which has twice as much methionine content as does groundnut cake on a per unit protein basis would be a more attractive buy at comparable prices.

These kinds of comparisons are only valid if the nutrient in one feedstuff is as valuable or available to the animal as the same nutrient in another feed. Such comparisons should be made whenever prices change.

Table 1

Worksheet for Diet Formulation

Name

Fish 452

Exercise

Balancing Rations

Balancing a ration for crude protein is only the first step in satisfying the protein requirement for a fish. Further attention must be paid to the amino acid content of the ration. The energy content of the ration must be calculated and be equal to the requirement of the animal.

a) Using the NRC Bulletin Nutrient Requirements of Trout, Salmon, and Catfish. Tables 5 and 6, balance a ration (Metabolizable energy and Crude Protein) for Coho salmon fry at S.F.T. Use Hydrolyzed Feather Meal, Corn Distillers Dried Solubles, and Wheat Middlings. Remember to reserve 3% of the total ration for vitamin supplementmentatin, which is assumed to contain no ME or CP. Express the quantities of each fixed as a percent of the total ration for number of Kg. in each 100 Kg mixturer. Express ME as Kcal/Kg of final ration and CP concentration in % of final ration.

Tolerences : Total Crude protein must meet minimum requirement and not be more than 0.5% over, since protein is costly. Total ME must be within 100 kcal of the requirement, either under or over.

b) Calculate the amino acid levels (ARG, LYS, MET and TRY) as a percent of the final ration. Use the content data given in the table below.

c) Using the amino acid requirements given below, compare these requirements with the ration composition (Part b) show the amount of excess or deficit of each. Which is the first most limiting amino acid ? MET. Second most limiting ? LYS

Besure to convert the amino acid levels in the ration to a % of the protein basis, since that is how the requirement is given below.

* Example of how to calculate are amino acid as a % of the protein. Feather meal arginine (% of the protein)

d) From the amino acid composition of some common fish feeds (Table 6) in your NRC bulletin, which of the protein supplements listed there contains the deficient amino acid(s) in the greatest concentrations (on a % of protein basis)? List 3 or 4. Feather meal is calculted for comparison.

e) Using one of the above protein supplements containing the deficient amino acids in the greatest concentration, reformulate the ration (part a) in order to correct the amino acid deficiencies (part c). Include only enough of one of the protein supplements in part d to balance the deficient amino acids. Do not completely replace feather meal in the ration. Crude protein and ME must remain balanced within constraints listed in Table a.

Table E. Rebalancing for ME and CP

f) Recheck levels of amino acids likely to be limiting :

Feed	% of ration	% ARG		% LYS		% MET		% TRY
		Product	Mix	Product	Mix	Product	Mix	Product	Mix
Feather meal	24	6.28	1.51	2.13	0.51	.64	0.15	.53	0.13
Corn Dis. Sol.	23	1.21	0.28	.99	0.23	.52	0.12	.31	0.07
Fish Meal (Herring)	20	4.34	0.87	7.93	1.59	2.17	0.43	0.43	0.09
Wheat Middlings	30	.81	0.24	.57	0.17	.15	0.04	.16	0.05
Vitamin Mix	3.0
Total	100.0		2.9		2.5		.74
Requirement	% OF PROTEIN IN FEED
% OF PROTEIN			5.7		5.0		1.5		0.7
% OF REQUIREMENT

Feather Meal 38% of Ration

ME in Feed = 3536 kcal/kg×0.38 = 1343.7 kcal contributed to Feed
Crude Protein in Feed = 93%×0.38 = 35.3% protein contributed to Feed

Corn Distiller's Solubles 37% of Ration

ME in Feed = 3317 kcal/kg ×0.37 = 1227.3 kcal contribution
Crude Protein in Feed = 29.8% ×0.37 = 11.0 % contribution

Wheat Middlings 22% of Ration

Amino Acid Levels are calculated in the same way as crude protein above

	% of PROTEIN
	Arginine	Lysine	Methionine	Tryptophan
Requirement	6.0	5.0	2.0	0.5
Ration Level	6.04	2.6	0.92	0.66

Revised Formulation		ME in Feed (kcal/kg)	Crude Protein in Feed
Feather Meal	24%	3536×.24=848.6	93×.24 = 22.3
Corn Dist. Sol.	23%	3317×.23=762.9	29.8×.23 = 6.9
Herring Meal	20%	4432×.20=886.4	76.7×.20 = 15.3
Wheat Middlings	30%	1663×.30=498.9	18.9×.30 = 5.67
Vitamins

What do we do now ?

1. We do not want protein to be any higher.

2. Energy can be higher

3. We need to add a little more ARG and 30% more MET.

Reformulate:

1. Add more herring meal as this is the best source of MET. If we meet the MET requirement by adding herring meal, we will also meet the ARG requirement.

2. Increase the amount of herring meal in the formulation, and decrease the amount of feather meal to lower the protein content of the feed. Adjust other ingredients as needed.

How To Solve The Formulation Problem

The second formulation had the following % of ingredients and Specification

To meet the amino acid requirement for METHIONINE I need to increase the amount of herring meal and decrease the amount of feather meal.

How much should I increase the % of herring meal?

The Feed now contains .74% MET (1.5% of protein in a 50% protein feed). I need to have 1% MET (2% of protein in a 50% protein feed). 1.0-.74 = approx. 0.3

Herring Meal now contributes .43% of the MET (2.17×.20) in the feed. Assuming nothing else changes, I need to get .7% of the MET (.43+.3) in the diet from the herring meal. However, if I add herring meal, I must take out other ingredients. Add 0.1% (ie =total = 0.8) to cover loss when other ingredients are removed.

Set level of herring meal in new formulation to 37 % How much Feather Meal should be in the new formulation? Feather meal is not very well balanced, so decrease % by half (ie: now 24% - decrease to 12%)

We now have the following in our formulation:

We have 48% of the diet to make up using Corn Distiller's Solubles and wheat middlings. We need to obtain about 10% more protein and increase Kcal by about 1000.

Corn distiller's Sdubles has 100% more energy and 50% more protein than wheat middlings. To obtain 1000 kcal from these two ingredients to (decided 500 kcal to come from each) we need to use twice as much wheat middling as Corn Distiller's Solubles, since CDS has 2 kcal for every 1 kcal in the wheat.

Therefore try (⅔×48) of wheat and (⅓of 48) of CDS.=

32% Wheat and 16% CDS.

Our Formulation is now:

Our formulation is now meeting the MET requirement, but is too high in energy and protein. However, only a small adjustment is necessary Once again, consider that CDS has 100% more energy and 50% more protein than wheat middlings. What can we do?

If we decrease CDS by 2 % what will happen? Protein will drop 0.60 (ie. 29.8×.02) and ME will drop by 66 (ie: 3317×.02)

If we increase wheat middlings by 2% what will happen? Protein will rise 0.38 (ie: 18.9×0.02) and ME will rise by 33 (ie: 1663×0.02

50.35% - 0.6%+0.38% = 50.13% CP if CDS down 2% and Wheat is up 2%

3127 Kcal ME - 66kcal + 33kcal=3094 kcal/kg

THIS WILL MEET REQUIREMENTS-

Work out complete nutrient balance for CP, ME and 4 amino acids.

% of MET Requirement met = 1.02/50.14 = 2.03 = 102% of Requirement
% of ARG Requirement met = 3.15/50.14 = 6.3 = 105% of Requirement
% of LYS Requirement met = 3.52/50.14 = 7.01 = 140% of Requirement
% of TRP Requirement met = 0.58/50.14 = 0.58 = 116% of Requirement

2nd Revised Formulation

ANALYSIS OF FORMULATION

ME (Kcal/kg) = 3093 needs to be in range 3000–3100

Crude Protein = 50.17% needs to be greater than 50% but not more than 0.5% over

% of Arginine Requirement met = 105 %
% of Lysine Requirement met = 140 %
% of Methionine Requirement met = 102 %
% of Tryptophan Requirement met = 116 %

Work through this formulation to see how final result was obtained.