4.1 Ingredient Types
4.2 Advantages of Compound Feeds
4.3 Physical Form of Diets
4.4 Choosing the Type of Compound Feed
So far this manual has dealt with the reasons why feeding fish and shrimp is advantageous. The major components of feedstuffs (lipid, protein, etc.,) have been described and an explanation of feed compositional tables has been provided. Now we come to the questions..... Which feed can I use? Do I have to use a mixture of feeds or will a single feedstuff do? What effect does the physical form of the diet have? As in the case of all of the topics in this manual, these questions are very broad. The manual aims to introduce the topics and to answer the questions in a preliminary way, leaving the reader to explore the subject further on his own. References on this subject are given at the end of the section in 'further reading'.
4.1.1 Grasses
4.1.2 Legumes
4.1.3 Miscellaneous Fodder Plants
4.1.4 Fruits and Vegetables
4.1.5 Root Crops
4.1.6 Cereals
4.1.7 Oil-Bearing Seeds and Oil Cakes
4.1.8 Feeds of Animal Origin
4.1.9 Miscellaneous Feedstuffs
4.1.10 Additives
There are ten major groups of materials which can be used in fish and shrimp/prawn feeds (Table 10). The categories given in Table 10 are those designed by Göhl (1981), plus an additional one, additives.
Table 10 Ingredient Categories
|
1. |
Grasses |
|
2. |
Legumes |
|
3. |
Miscellaneous fodder plants |
|
4. |
Fruits and vegetables |
|
5. |
Root crops |
|
6. |
Cereals |
|
7. |
Oil-bearing seeds and oil cakes |
|
8. |
Feeds of animal origin |
|
9. |
Miscellaneous feedstuffs |
|
10. |
Additives |
A summary of the major characteristics of each group is given below. Descriptions of some of the most common ingredients in each category are given in Appendix V; details of their analytical characteristics are given in Appendix IV. Excellent descriptions of over 500 animal and plant substances and their by-products are given in Göhl (1981); other papers on this topic are listed in 'further reading' at the end of section 4.
Grasses are normally utilized either fresh (as pasture) or in the form of hay or silage for cattle. Dried grass is also used in feeds for other livestock and is a potential minor ingredient in fish and shrimp feeds, as a source of carotenoids. Being characteristically very high in fibre content, grasses are of limited value in fish feeds except for herbivorous fish.
The leaves and stems of legumes are, like the grasses, widely used as fodder for terrestrial animals. A few (e.g., ipil-ipil and alfalfa) have successfully been used in feeds for aquaculture. Legume fodder is rich in protein and minerals. The seeds of legumes have a great potential value as aquaculture feed ingredients though many contain anti-nutritive factors when raw; processing (heat treatment) usually renders them safe for use. Leguminous seeds are often rich in lysine though poor in methionine. Whole beans and peas are used extensively as human food. They are therefore usually expensive ingredients and their use in aquaculture feeds may only be justified in diets for high-value export-oriented species. Some examples of leguminous plants, which all have the ability to convert gaseous nitrogen into protein, are acacia, clover, lucerne, groundnut (peanut), gram, lentil, locust beans, chickpea, guar, ipil-ipil, lima beans, field peas, mung bean, cowpeas, and soybean.
Some leguminous plants produce high-oil seeds which are processed for the extraction of vegetable oil. The by-products of oil extraction processes are included in section 4.1.7.
The leaves and other aerial parts of many plants, other than those specifically grown for fodder, are used for this purpose. While these may have local significance as aquaculture feed ingredients, nutrient digestibility (though crude protein levels on a DM basis are often quite high) is low. The plants in this category which have proved to be useful in aquaculture feeds are listed in Appendix V.
Waste fruits and vegetables and the by-products from their processing or harvesting have not been used much in compound feeds for aquaculture. However, they are sometimes used, fresh, for feeding or manuring ponds. As both types of products are usually seasonal, large quantities of wastes and by-products are available intermittently but they are not normally preserved for later use by ensiling or drying. The leaves of these plants are usually more nutritious than the stems. Examples of the many by-products in this category which are often wasted are those from grapes, tomatoes, the palms, bananas and plantains, mangos, melons, citrus fruits, pineapple, and breadfruit.
Root crops are excellent sources of energy for many classes of livestock, being rich in carbohydrates. Their value as ingredients for aquaculture feeds is limited however, partly because of their high value for human food and partly because most aquatic species cannot digest carbohydrates well. Root crops, with some exceptions, are very deficient in protein, calcium and phosphorus, and vitamins. Waste from root crops can be utilized in small quantities in compound feeds. Many contain toxins which need destruction by heating before use. Some root crops have special value in aquaculture because of their ability to increase the water stability of diets (see Appendix XII), e.g., potato, cassava (manioc; tapioca), and sugar beet molasses. Other plants in this category include yams, carrots, Jerusalem artichokes and dasheen (yaro).
Cereals and cereal by-products, despite their high carbohydrate content, form an important component in aquaculture diets. Their starch content helps to increase the water stability of the feed, particularly where heat is included in their method of processing. Cereals also contribute significantly to the protein and lipid content of the diet. Though deficient in some amino acids (e.g., lysine) they can be used to balance high-protein animal and vegetable ingredients. Cereals are often one of the cheapest raw materials that can be included in compound feeds for aquaculture. The brans are excellent sources of the B group vitamins. The names of cereal grains are well known. Examples, particularly of their by-products are however given in Appendix V.
Many plants are grown specifically for the oil which their seeds or fruits produce, which is utilized for human food and other purposes. Vast quantities of by-products from the vegetable oil industry are produced and these are the staple ingredients of animal feedstuffs, being high in protein and low in carbohydrate. All are potential ingredients of aquaculture feeds.
Examples of the plants from which products in this category come are the leguminous plants soybean and groundnut, together with mustard, rape, sunflower, safflower, coconut, kapok, cotton, oil palm, linseed, poppy, sesame (gingelly) and para rubber (caoutchouc).
In considering the use of ingredients from this group it is essential to understand the terminology used in describing oil-seed by-products because ingredients with apparently similar names have completely different analytical characteristics. The external coating of some seeds is sometimes but not always completely removed before oil extraction, e.g., in the case of sunflower seed, groundnut, and cotton seed. The material which remains after oil extraction is referred to in several ways:
|
Decorticated (sometimes referred to as 'Dec') |
Coating removed before oil extraction |
|
De-hulled |
Coating removed before oil extraction |
|
Without hulls |
Coating removed before oil extraction |
|
(Undecorticated (shortened to 'Undec') |
Coating not removed |
|
With hulls |
Coating not removed |
Some intermediary products between 'Dec' and 'Undec' exist. A few tables of feed composition (e.g., NAS, 1971) refer to these as 'with some hulls'. Decorticated products are higher in protein and lower in fibre than undecorticated products.
The other major set of terms applied to this class of feeds refer to the method of oil extraction used, which also has important analytical consequences. These terms are defined as follows:
Expeller: (shortened to 'Exp'):
oil removed by mechanical process, either by hydraulic presses or by screw augers. The latter type can be distinguished by looking at the pieces of unground cake, which are not flat. The hydraulic process does not remove as much oil but damages the cake less than the screw process which generates a lot of heat.
Extracted: (shortened to 'Ext')
oil removed by a highly efficient chemical process using solvents. Sometimes the words 'solvent extracted' are applied to this residual product.
The characteristics of these products are that expeller residuals are much higher in oil content and lower in protein content than extracted products.
Two other terms are applied to oil-seed residues. These are 'cakes' and 'meal'. Normally, if a product is referred to as a 'cake' it means it is an expeller residue. Similarly a 'meal' normally refers to an extracted product. However there can be some confusion here because the word 'meal' can also be used to refer to a ground or milled product. So, the words 'groundnut meal' might refer either to groundnut cake which had been ground into a meal or it might refer to extracted groundnut. When in doubt, the chemical analysis is the only criterion to use in determining which product is being offered for sale if it is in ground (meal) form. Some illustrations of the important analytical differences designated by the above terms are given below in Table 11.
Table 11 Examples of the Effect of Processing on Analytical Characteristics of Oil-Seed Proteins
|
Country and Material |
H2O |
LIP |
PROT |
FIB |
NFE |
ASH |
|
Pakistan | ||||||
|
Dec. Cottonseed |
7.3 |
5.2 |
36.7 |
8.8 |
34.9 |
7.1 |
|
Undec. Cottonseed |
6.5 |
8.9 |
21.5 |
24.5 |
32.5 |
6.1 |
|
USA | ||||||
|
Exp. Groundnut |
10.8 |
7.3 |
45.1 |
6.8 |
24.7 |
5.3 |
|
Ext. Groundnut |
8.5 |
1.2 |
47.4 |
13.1 |
25.3 |
4.5 |
Note: The squares denote the analytical component most affected by the processing differences between the alternatives in each pair of ingredients.
Oil seed hulls are also available by-products of the vegetable oil industry but, being extremely high in indigestible fibre content, are of little value for aquaculture feeds.
Descriptions of the common oil-seed residues are to be found in Appendix V.
These ingredients are either from terrestrial, avian or marine animals. They constitute the most important (and often the most expensive) ingredients of aquaculture feeds. Animal protein is necessary to balance the amino acid and vitamin deficiencies in cereals and other plant products. Animal proteins appear to contain unidentified growth factors for some animals. Marine proteins have always been important components of aquaculture diets although shortages of fish meal are stimulating research on methods of replacing them, either partially or completely, with other ingredients. Ingredients of marine origin are important sources of poly-unsaturated lipids (PUFA's), particularly of the important n-3 series (see section 3.1.2). Some examples of ingredients in this category are blood, feather meal, poultry by-products meal, fish meal, meat meal, raw fish, fish oils, fish silage, shrimp meal and milk by-products. Some of the more common of these ingredients are described in Appendix V.
Many other ingredients have potential in aquaculture feeds; their value has not yet been fully evaluated, however. Some of these ingredients are sometimes referred to as 'unconventional' or 'non conventional' feedstuffs, though many, such as cane sugar molasses, are conventional ingredients in feedstuffs for other animals. This group of feedstuffs includes leaf protein concentrate, minerals, seaweed, by-products of sugar cane, by-products of fermentation processes, lipids, microbial proteins, algae, manures, and celluloses. Some examples are described in Appendix V.
An increasing diversity of other substances are being used in animal feedstuffs. These include synthetic amino acids, vitamins, binders, antioxidants, preservatives, prophylactic medicines, hormones, and growth promotors. Most of these have very specific uses, for which manufacturers' literature should be consulted. It is beyond the scope of this manual to deal with this topic in detail but some comments or definitions are given below:
|
Amino Acids |
The major synthetic amino acids available for supplementation are 1-lysine and dl-methionine (see section 3.1.3.). See also 'chemo-attractants' below. |
|
Vitamins |
Individual vitamins, or premixes of them prepared for specific purposes, are commercially available. The storage and mixing of vitamins, and other trace substances, require special care and facilities and it is not recommended that farmers prepare their own or attempt to add individual synthetic vitamins to their feeds. Where this is done, however, it is essential to dilute the substance before adding it to the final product (see section 5.4.5.). |
|
Binders |
Substances used to improve the durability (preserve the physical form of the diet during storage e.g., prevent pellets breaking down into 'fines') or the water stability of the feed are dealt with in Appendix XII. |
|
Antioxidants |
Usually included in vitamin premixes or added to lipids (especially fish oils) during manufacture, antioxidants are substances capable of preventing or delaying the onset of rancidity. Feed rancidity results in the unpalatibility of feeds and the generation of toxic chemicals. Antioxidants can be naturally occurring substances, such as vitamin E, or synthetic chemicals. The commonly available commercial antioxidants, under a variety of trade names, are BHT (butylated hydroxytoluene), BHA (butylated hydroxyanisole) and ethoxyquin. |
|
Preservatives |
Several substances may be added to feeds to control the rate of deterioration, particularly that due to fungal attack. Most are sodium or potassium salts of propionic, benzoic, or sorbic acid. |
|
Chemo-attractants |
Synthetic chemicals or natural ingredients containing chemicals, such as free amino acids which cause feeding behaviour in fish or shrimp. Meyers (1987a) has reviewed this topic, which is also covered by Mackie and Mitchell (1985) |
Feed ingredients can be fed singly or in simple or complex mixtures. The latter are usually known as compound or compounded feeds. They are sometimes fed simply as a meal or mash (mixed ground ingredients), or in some form of dry pellet, or as a formed moist product (see section 4.3).
Though feeding of single ingredients to fish and shrimp is often practised it can be a very inefficient use of feed because a single ingredient is most unlikely to supply all the nutrients required by the animal in the balance in which it needs them. Unless the system of culture is so intense that the contribution of natural food is minimal, single ingredients often act more as. a manure which increases natural productivity, than a specific feed for the animal being cultured.
A single feed ingredient may, for example, be too high in indigestible fibre which may be largely wasted, or in carbohydrate of limited digestibility. Conversely, the ingredient may be too high in expensive protein which may be consumed to satisfy the energy requirement of the animal rather than for growth (see section 3.1.5.).
The unsatisfactory nature of feeding single feedstuffs to fish is partly responsible for the generally poor apparent feed conversion ratios (AFCR's) achieved by doing so (note that compound feeds for fish usually give AFCR's of 2.0-2.5, or less). Table 12 illustrates this point:
Table 12 Apparent Feed Conversion Ratios (AFCR) 1/achieved by Feeding Single Ingredients to Fish
|
Ingredient |
AFCR 1/ |
|
Fresh sea fish |
6-9 |
|
Freshwater fish |
2.9-6.0 |
|
Fresh meat |
5-8 |
|
Prawns and shrimp |
4-6 |
|
White cheese |
10-15 |
|
Soybeans |
3-5 |
|
Maize (corn) meal |
3.5 |
|
Potatoes |
20-30 |
|
Cottonseed cake |
3 |
|
Ground rice |
4.5 |
|
Oil palm cakes |
6-12 |
|
Cassava leaves |
10-20 |
|
Guinea grass |
48 |
|
Banana leaves |
25 |
|
Dried silkworm larvae |
1.8 |
Source: Hickling, 19621/ For explanation of AFCR, see section 2.5.2 of this manual. Some of the ingredients are moist, which also reduces their AFCR on an as-fed basis.
The effect of feeding a single ingredient versus simple mixtures of ingredients can be illustrated as follows, using only the lipid, protein and fibre levels as examples. Suppose we consider four ingredients only - wheat, rice bran, expeller groundnut cake and fish meal. It is very unlikely that fish meal would ever be used as a single feedstuff because of its cost - it is used in this example for illustrative purposes only. For the purpose the analysis of the four materials is assumed as follows:
|
Ingredient |
Lipid (%) |
Protein (%) |
Fibre (%) |
|
Rice bran |
4.9 |
12.5 |
18.3 |
|
Fish meal |
6.0 |
55.0 |
2.4 |
|
Exp. Groundnut |
11.5 |
37.7 |
13.2 |
|
Wheat |
1.5 |
12.2 |
2.7 |
If the dietary requirements of the fish being cultured are assumed as 6% lipid, 23% protein and less than 8% fibre the effect of feeding any of the four ingredients can be demonstrated as follows:
|
Effect of Feeding Single Ingredients | |||
|
Ingredient |
Lipid |
Protein |
Fibre |
|
Rice bran |
82 |
54 |
229 |
|
Fish meal |
100 |
239 |
30 |
|
Exp. Groundnut |
192 |
164 |
165 |
|
Wheat |
25 |
53 |
34 |
|
(Dietary requirement = |
6.0 |
23.0 |
<8.0) |
It can be seen at once that, in the above example, none of the ingredients complies with the dietary requirements of the animal. Wheat supplies neither enough lipid nor protein, although it does not exceed the maximum fibre level which was set. Expeller groundnut supplies too much of all three components when fed alone. The fish meal complies with the maximum fibre level imposed but is in gross and wasteful excess in protein level. The rice bran is deficient in lipid and protein and very much in excess of the desired fibre content.
Even a simple 60:40 mixture of two of the ingredients in the above example results in a product which is much closer to the requirements of the animal defined for this example:
|
Inclusion Level of Ingredient |
Contribution to Mixture |
||
|
Lipid (%) |
Protein (%) |
Fibre (%) |
|
|
60% Rice Bran |
2.94 |
7.50 |
10.98 |
|
40% Exp. Groundnut |
4.60 |
15.08 |
5.28 |
|
Total |
7.5 |
22.6 |
16.3 |
|
(Dietary requirement = |
6.0 |
23.0 |
<8.0) |
The 60:40 mixture of rice bran and expeller groundnut cake now complies with the dietary protein requirements of the animal and is only a little in excess in lipid. It still contains too much fibre but it is a great improvement on either ingredient used singly.
One of the ways in which these four ingredients could have been used to achieve greater compliance with the dietary requirements which were set for the animal would have been to have used 20% rice bran, 35% exp. groundnut, 5% fish meal and 40% wheat. The result would have been as follows:
|
Inclusion Level of Ingredient |
Contribution to |
Mixture |
|
|
Lipid (%) |
Protein (%) |
Fibre (%) |
|
|
40% wheat |
0.60 |
4.88 |
1.08 |
|
20% rice bran |
0.98 |
2.50 |
3.66 |
|
35% exp. groundnut |
4.03 |
13.20 |
4.62 |
|
5% fish meal |
0.30 |
2.75 |
0.12 |
|
Total |
5.9 |
23.3 |
9.5 |
|
(Dietary requirement = |
6.0 |
23.0 |
<8.0) |
The mixture of four ingredients is still rather high in fibre but complies well to the requirement for lipid and protein.
Thus the purpose of a mixed or compound diet is demonstrated - it is to provide a feed which is balanced in its various components. In practice these include a wider variety of components than the three illustrated in the above example. The topic of formulation will be dealt with more thoroughly in section 5.2 of this manual.
The emphasis in the rest of this manual will therefore be on the formulation, production and use of compound feeds for aquaculture.
Mixed or compound feeds may be presented to fish or shrimp in a number of different forms.
The feed may be dry (about 10% moisture), moist (about 30-45% moisture) or wet (>50% moisture) or an intermediate between these. Normally, only mixtures of wet materials (e.g., trash fish) would come into the wet category. Most compounded aquaculture feeds fall into the dry category or the moist group.
Dry feeds are easier to manufacture on a large scale and easier to store, transport and feed. There is evidence however that moist feed may be more palatable and attractive to the animals and can give better results than a dry feed. Moist feeds are easily made on a small scale at the farm site. There is the additional advantage that moist ingredients (e.g., trash fish) can be utilized without employing energy wasting, and sometimes quality damaging techniques of fish meal production. Dry feeds lend themselves to large-scale manufacture best, though there are some commerically available moist feeds for fish (and many more for pet animals). The topic of feed manufacture is discussed in section 5 of this manual.
Dry and moist feeds are usually formed into a definite physical shape - pellets, crumbles, granules, balls, cakes, etc. Dry pellets are normally tubular in shape with a fixed length and diameter. Their diameter depends on the size of the orifice through which they are extruded. Usually, dry pellets are cut by the pelleting machine into pre-selected lengths. Dry pellets can be broken into smaller irregular shaped particles - crumbles -or reduced still further in size and graded into various sized granules for younger animals. The hardness of pellets may be varied by manufacturing technique, choice of ingredients, and the use of binders.
Moist feeds are normally extruded through some form of mincer to form pellets of regular diameter, depending again on the diameter of the size of orifice through which they are extruded. Moist pellets are often not cut so they break naturally from a spaghetti or noodle-like product into a range of pellet lengths. Maintenance of their shape in air and in water depends on the choice of ingredients, method of manufacture and on the use of binders. Some moist feeds consist of hand-made compacted cakes or balls of feed.
The particle size of raw materials is also important for it governs the durability and acceptability of the compound feed it is included in. Generally, finer particles make better pellets but poor grinding techniques can damage the nutritional quality of the feed.
Compound feeds can also be made in a 're-hydratable' form. These are dry pellets which rapidly absorb water when placed in water (i.e., when fed) and become soft, like a moist feed.
Feeds produced by the moist feed technique can, if desired, be sun-dried into dry feeds and stored and fed in the same manner as the latter.
Feeds can be produced that sink to the bottom of the pond, tank or cage (most compound feeds are of this type) or they can be manufactured in a way that produces a floating pellet. The latter have the advantage, for those fish that will accept them, that it is easier to observe when feeding occurs and when all the feed is consumed. Shrimp do not accept floating feeds well, except when they are very young post-larvae at which time they are still mainly pelagic in habit.
Commercial aquaculture feeds are produced in a range of sizes designed for different sizes (ages) of animals. Examples of the sizes used are given in tables 13-17 and in Appendix XIII.
Information on particle size determination is given in Appendix XI.
Different species of shrimp and fish have different nutritional requirements, both in terms of the type of raw materials used (quality) and the proportion (quantity) of each component ingredient. The requirements vary because of the characteristics of the species being cultured which are affected by its normal diet in its natural environment. Specifications for the major species covered by this manual are given in section 6. Methods for making different types of feed are given in the next section, section 5. Final selection of the type of feed to use will depend on the size and behaviour of the animal to be fed, the type of production unit it is to be reared in, the availability of labour and feed manufacturing equipment, and economics.
Further reading (for section 4)
Göhl (1981); Kennedy (1978); Malik and Chughtai (1979); Sadiq and Seng (1982); Devendra (1981); Jauncey and Ross (1982); ADCP (1983); ADCP (1980); Manik et al., (1977); Minsaas (1978); Lovell (1982); Boonyaratpalin (1982); Deveraj and Keshavappa (1980); Edwards (1982); Viola et al., (1981); Viola and Arieli (1983); Jackson et al., (1984); Disney and James (1980); Tacon (1981); Tacon (1985); Brandt (1979); Rumsey et al., (1981); ADCP (1979); Woynarovich and Kühnhold (1979); Müller (1980); NRC (1983); Piper et al., (1982); Phillips (1970); Tacon and Jackson (1985).
Table 13 Feed Sizes for Trout
|
Animal Size |
Feed Size |
|
Fry from swim-up to 3 inch |
Crumbles (size unspecified) |
|
3-4 inches |
Pellets 3/32 × 3/32 inches long |
|
4-7 inches |
Pellets 1/8 × 1/8 inches long |
|
> 7 inches |
Pellets 1/4 × 1/4 inches long |
Source: Phillips, 1970
Table 14 Standard Granule and Pellet Sizes for Salmon and Trout
|
Size |
Specification 1/ |
Notes |
|
Granules | ||
|
Starter |
420-595 microns |
Made from 1/8 inch pellets |
|
No. 1 |
595-841 microns |
Made from 1/8 inch pellets |
|
No. 2 |
841 microns-1.19 mm |
Made from 1/8 inch pellets |
|
No. 3 |
1.19-1.68 mm |
Made from 3/16 inch pellets |
|
No. 4 |
1.68-2.38 mm |
Made from 3/16 inch pellets |
|
No. 5 |
2.38-3.36 mm |
Made from 3/16 inch pellets |
|
Pellets | ||
|
3/32 × 3/32 inch |
2.35 × 2.35 mm |
|
|
1/8 × 1/8 inch |
3.1 × 3.1 mm |
|
|
3/16 × 3/16 inch |
4.7 × 4.7 mm |
|
|
1/4 × 1/4 inch |
6.25 × 6.25 mm |
|
Source: NRC, 1981
1/Micron size is determined by particle analysis (see Appendix XI)
Table 15 Feed Sizes for Rainbow Trout (in Japan)
|
|
Fish Size |
Food Type |
Feed Size |
|
(g) |
(mm) |
||
|
Fry |
<0.5 |
Crumble (C) |
0.3-0.5 (300-500 microns) |
|
0.5-1.5 |
C |
0.5-0.9 |
|
|
Fingerling
|
1.5-5.0 |
C |
1.0-1.4 |
|
5.0-10.0 |
C |
1.5-2.5 |
|
|
Adult |
10-15 |
Pellet (P) |
2.4 |
|
15-40 |
P |
3.2 |
|
|
40-200 |
P |
4.4 |
|
|
200-400 |
P |
6.0 |
|
|
>400 |
P |
8.0 |
|
|
Spawner |
>400 |
P |
8.0 |
Source: Kafuku and Ikenoue, 1983
Table 16 Recommended Particle Sizes for Channel Catfish Fry
|
Weight of Fish |
Feed Size |
|
(g) |
(mm) |
|
0.02 - 0.25 |
0.42 - 0.84 |
|
0.25 - 1.5 |
0.85 - 1.4 |
|
1.5 - 5.0 |
1.4 - 2.8 |
|
5.0 -20.0 |
2.8 - 4.0 |
Source: NRC, 1983
Table 17 Recommended Sizes for Abernathy Dry Pellets for Pacific Salmon
|
Fish Size |
Feed Size |
|
(g) |
|
|
<0.57 |
Starter granule |
|
0.57-0.91 |
1/32 inch granule (G) |
|
0.91-2.27 |
3/64 inch G |
|
2.27-4.54 |
1/16 inch G |
|
4.54-6.05 |
3/32 inch G |
|
6.05-9.08 |
3/32 inch pellet (P) |
|
9.08-22.7 |
1/8 inch P |
|
>22.7 |
3/16 inch P |
Source: Piper et al., 1982
