3. NUTRIENT SOURCES - COMPOSITION OF FEEDSTUFFS AND FERTILIZERS (cont.)

3.3 Grain legumes

Grain legumes, or pulses, are plant species belonging to the family Leguminosae which are cultivated for their mature seed or immature green pods, and include the bambara groundnut, broad bean, chick pea, cluster bean, cowpea, grass pea, haricot bean, horse gram, hyacinth bean, jack bean, kersting's groundnut, lentil, lima bean, lupin, mung bean, pea, pigeon pea, rice bean, runner bean, sword bean, urd, velvet bean, and winged bean. The two oleaginous legume crops, groundnut (A. hypogaea) and soybean (G. max), which are grown primarily for processing into edible oils and protein concentrates, have been discussed previously in section 3.2 under oilseeds and by-products.

Grain legumes are good sources of protein (average protein content of the dry seed being 20–26%), energy (either in the form of lipid or starch carbohydrates), and several B vitamins (ie. thiamine, riboflavin, and nicotinic acid). The grain legumes are often considered as natural supplements to the cereal grains, since, although they are usually deficient in the sulphur amino acids methionine and cystine, they contain adequate amounts of lysine (cereal grains being deficient in lysine but usually containing adequate methionine and cystine; Tacon, 1987). The average proximate and essential amino acid composition of the major grain legumes and their by-products is shown in Table 11 and 12 respectively.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Bath et al., (1984); Bolton and Blair (1977); Branckaert, Tessema and Temple (1976); Cooley (1976); Devendra (1979); Gohl (1981), Hickling (1971); Kay (1979); Ling (1967); NRC (1982, 1983); Platt (1962); and Springhall (1969).

¹ The data presented represents the mean values from various sources including: Allen (1984); Bolton and Blair (1977); FAO (1970); Kay (1979) and NRC (1982).

3.4 Root crops

Root crops are those plant species which have extensive carbohydrate food reserves in their underground stems (ie. tubers) or roots, and include the taro, mangold, carrot, turnip, swede, arrowroot, yam, jerusalem artichoke, sweet potato, cassava, oca, yam bean, yacón, kudzu, radish, arrowhead, potato and cocoyam.

Root crops and tubers are poor sources of protein (2–10% dry weight; a large proportion of which is in the form of non-protein nitrogen), vitamins, calcium and phosphorus, but are rich dietary sources of potassium and digestible carbohydrates; the latter being in the form of sugars within root crops and fructans or starch within tubers. As with most plant feedstuffs, roots and tubers may also contain a variety of endogenous anti-nutritional factors, which, unless destroyed or inactivated, can seriously reduce their feed value to fish or shrimp (Table 2). The average proximate and essential amino acid composition of the major root crops and their by-products is shown in Table 13 and 14 respectively.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Bath et. al., (1984); Bolton and Blair (1977); Branckaert, Tessema and Temple (1976); Cooley (1976); Devendra (1979); Gohl (1981); Hastings (1973); Hickling (1971); Kay (1973); MacDonald, Edwards and Greenhalgh (1977); Miller (1976); NRC (1982); and Platt (1962).

¹ The data presented represents the mean values from various sources including: Allen (1984); FAO (1970) and NRC (1982)

3.5 Fruits

Many plant fruits and their process by-products may be considered for animal feeding. Although fruits are generally regarded as poor dietary sources of protein, vitamins (with the possible exception of vitamin C) and minerals, they are rich sources of digestible carbohydrate and therefore energy. The average proximate and essentialamino acid composition of the major edible fruits and their by-products is shown in Table 15 and 16 respectively.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Bath et.al., (1984): Branckaert, Tessema and Temple (1976): Cooley (1976); Gohl (1981); Janseen (1985): Ling (1967); Miller (1976); NRC (1982); Platt (1962); Springhall (1969); and Tacon (1986).

¹ The data presented represents the mean values from Allen (1984) and NRC (1982).

3.6 Grass, green crops, and miscellaneous plant feedstuffs

Grass and forage crops constitute a valuable source of dietary carbohydrates, protein, vitamins and minerals. These crops may be utilized as feeds either in their natural (ie. fresh) state or in their conserved state. Two processing methods are commonly employed for conserving (ie. storing) green crops, ‘hay-making’ and ‘ensilage’.

Hay-making is the commonest method of conserving green crops. Here the moisture content of the fresh crop is reduced from 65–85% to 15–20% by drying the crop under the sun or by using artificial drying techniques (ie. barn drying equipment). The essence of hay-making is to reduce the moisture content of the crop to a level low enough to inhibit the action of plant and contaminating microbial enzymes. For practical reasons, the crop is normally harvested for hay-making when its moisture content is at its lowest (ie. at maturity, or in the early flowering stage for grasses). Straw, on the other hand, consists of the stems and leaves of plants after the removal of the ripe seeds by threshing, and are produced from most cereal crops and from some legumes. Chaff consists of the husk or glumes of the seed which are separated from the grain during threshing.

Ensilage is a conservation method which relies on the controlled bacterial fermentation of the wet crop. The fermentation is controlled either by encouraging lactic acid formation by bacteria present on the fresh herbage, or by direct addition of acid solutions or chemical preservatives (the acidity prevents spoilage of the ensiled material). Crops which particularly lend themselves to ensiling include grass, grass-clover mixtures, legumes, green cereals, root tops, sugar beet pulp and fruit residues. For a review of these conservation methods see McDonald, Edwards and Greenhalgh (1977).

The average proximate and essential amino acid composition of grass, green crops, and some selected miscellaneous plant feedstuffs is shown in Table 17 and 18 respectively.

¹ The data presented represents the mean values from various sources including: Allen (1984); Bath et. al., (1984); Brackaert,Tessema and Temple (1976); Cooley (1976); Devendra (1979); Gohl (1981); Hickling (1971); Kay (1973, 1979); Ling (1967);MacDonald, Edwards and Greenhalgh (1977); Miller (1976); NRC (1982); Ogino, Cowey and Chiou (1978); Tacon (1983; 1986).

² Data presented for pasture grass was obtained from McDonald, Edwards and Greenhalgh (1977); for specific speciescomposition see Gohl (1981) and NRC (1982).

¹ The data presented represents the mean values from various sources including: Allen(1984); Bolton and Blair (1977); FAO (1970); NRC(1982, 1983); Ogino, Cowey and Chiou (1978), and Tacon (1983)

3.7 Vascular aquatic macrophytes

Vascular aquatic plants or macrophytes constitute a potentially valuable source of dietary nutrients for omnivorous/herbivorous aquaculture species. Although the high water content of aquatic macrophytes (ie. range 75–95%) may be undesirable from an economic viewpoint when used as a dried feed for terrestrial farm animals (ie. high cost of dewatering), this would not be the case for aquaculture species cultured under semi-intensive pond rearing conditions where such products could be utilized in their fresh state as a whole or chopped supplementary feedstuff. In general aquatic macrophytes are poor sources of dietary protein (range 0.7–3.5% protein, fresh basis) and lipid, but are regarded as good sources of digestible carbohydrate and minerals (ie. calcium, potassium, magnesium and the trace elements). In common with terrestrial land plants, vascular aquatic macrophytes may contain considerable amounts of crude fibre and in particular anti-nutritional factors such as tannins. For a comprehensive review of the nutritive composition and value of aquatic macrophytes see Boyd and Scarsbrook (1975), Edwards (1980) and Little (1979).

The average proximate and essential amino acid composition of the major aquatic macrophytes which have been utilized or tested for aquaculture feeding is shown in Table 19 and 20 respectively.

¹ The data presented represents the mean values from various sources including: Boyd (1968, 1969, 70); Carraro (1983);Edwards, Kamal and Wee (1985); Gohl (1981); Ling (1967); Linn (1975); Little (1979); Little and Henson (1967); Pullin andAlmazan (1983); and Siriwardene, Ranawana and Piyasena (1970).

² Carraro (1982) reports composition of Azolla sp. as 23.4% crude protein, 22.1% cellulose, 11.3% hemicellulose,23.0% lignin and 14.5% ash on a dry matter basis.

³ Composition reported in the literature reviewed was highly variable, crude protein ranging from 4.5 to 17.5% and ashranging from 5.6 to 41.2% on a dry weight basis.

⁴ Data obtained from the study of Siriwardene, Ranawana and Piyasena (1970), although Little and Herson (1967) report thewater content of the fresh whole plant as 92.8%.

⁵ Data for crude fibre and nitrogen-free extractives reported together (Ling, 1967).

¹ The data presented represents the mean values from various sources including: Boyd (1968, 1969) and Carraro (1983).