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4.1 Dietary essential mineral deficiency

Table 5 shows the major anatomical deficiency signs which have been reported in fish fed rations deficient in one or more essential minerals. Despite the presence of macro and micro (trace) elements in virtually all raw ingredients commonly used for fish feeding (Tacon & De Silva, 1983) and the ability of fish to absorb certain trace elements from the surrounding water, mineral deficiencies may arise under intensive culture conditions through:

For certain fish species the availability and absorption of phosphorus and other major elements (calcium) from fish meal and meat and bone meal is further complicated by the absence of an acid-secreting stomach, which is essential for normal bone solubilization. For stomachless fish species soluble monobasic inorganic salts or bioavailable organic salts must therefore be provided in the diet. Conversely, within plant proteins a large proportion of phosphorus is present as organically bound phytates. Not only is phytic acid phosphorus largely biologically unavailable, but phytic acid also has the capacity to chelate other trace elements (ie. iron, copper, zinc, cobalt, molybdenum) and by so doing may render them biologically unavailable to the fish during digestion (Spinelli, 1980; Lovell, 1989; Hossain & Jauncey, 1991). For example, in channel catfish (I. punctatus) dietary phytate has been shown to reduce the bioavailability of zinc, especially in the presence of high dietary calcium (Gatlin & Phillips, 1989). Furthermore, high dietary phytate levels (2.2%) have also been reported to have a negative effect on fish growth and feed efficiency in channel catfish (Satoh, Poe & Wilson, 1989).

Under practical farming conditions mineral deficiency signs often arise from a dietary imbalance of calcium; due to the antagonistic effect of excess dietary calcium on the absorption of phosphorus (Nakamura, 1982) and the trace elements zinc, iron and manganese (Lall, 1979). For example, the bioavailability of zinc and to a lesser extent manganese and magnesium, within white fish meal has been found to be much lower than that contained in brown fish meal (which has a much lower ash and calcium content; Ketola, 1978; Watanabe, Takeuchi & Ogino, 1980; Satoh, Takeuchi & Watanabe, 1987a, 1987b, 1991). Similarly, increasing levels of dietary calcium phosphate (Ca3(PO4)2 and Ca(H2PO4)2) was found to have a inhibitory effect on zinc bioavailability in rainbow trout, inducing short body dwarfism or eye cataracts (Satoh et al. 1987, 1991). It is perhaps not surprising therefore that rainbow trout, chum salmon and common carp fed on diets in which white fish meal was used without a trace element supplement that overt trace element deficiency signs arise, including reduced growth, short body dwarfism and cataracts (Watanabe, Takeuchi & Ogino, 1980; Satoh et al. 1983, 1983a; Yamamoto et al. 1983; Watanabe, Satoh & Takeuchi, 1988). Furthermore, recent trials concerning the dietary zinc requirements of channel catfish (I. punctatus) swim-up fry in soft and hard water appear indicate that environmental calcium interacts with dietary zinc and may also fry growth and survival (Scarpa & Gatlin, 1992). However, the recent trials of Satoh et al. (1991) also suggest that high dietary intakes of phosphorus (1.8% of diet) also has a negative effect on growth and zinc availability, thus indicating the importance of the balance between dietary calcium and phosphorus; the best growth reported for rainbow trout fed calcium and phosphorus in equal proportions.

4.2 Dietary mineral toxicity

A major hazard which may be associated with the use of unconventional dietary feed ingredients is the presence of heavy metal contaminants including the accumulative elements copper, lead, cadmium, mercury, arsenic, fluoride, selenium, molybdenum and vanadium. For example, contamination with copper may arise from products fermented within copper lined vessels (brewery by-products), or within pig and poultry excreta from the use of copper based growth stimulants and anti-fungal agents. Other feed ingredients which may contain metal contaminants include: poultry waste - arsenic; paper pulp waste -lead; fish meals - mercury, selenium, arsenic cadmium and lead; poultry by-product meals - zinc; hydrolysed feather meals - zinc; shellfish - zinc, cadmium; seleniferous accumulating plants of the genera Astragalus and Machaeranthera, or cereals grown in seleniferous soils - selenium; krill meal - fluoride. Table 7 lists the major toxicity signs which have been reported in fish under laboratory conditions.

Table 5. Reported essential mineral deficiency signs in fish
Element/fish sp.Deficiency signs1
C. carpioReduced growth, poor feed efficiency (1,2), bone demineralization, skeletal deformity, abnormal calcification of ribs and the soft rays of the pectoral fin (1), cranial deformity (1,3), increased visceral fat (4)
I. punctatusReduced growth, poor feed efficiency (5), bone demineralization (5,6)
P. majorReduced growth, poor feed efficiency, bone demineralization, increased muscle, liver and vertebrae lipid content (7), curved and enlarged spongy vertebrae (8), decreased liver glycogen (9)
A.japonicaAnorexia, reduced growth (10)
O.mykissReduced growth, poor feed efficiency, bone demineralization (13,14)
S. salarReduced growth, poor feed efficiency, bone demineralization (13,14)
I. punctatusReduced growth, low carcass ash, Ca and P content (fed vitamin D deficient diet, 6)
O. mykissAnorexia, poor growth and feed efficiency (15)
A.japonicaAnorexia, poor growth and feed efficiency (16)
P.majorAnorexia, poor growth and feed efficiency (17)
O. tshawytschaReduced growth and feed efficiency, anorexia, convulsions, tetany, death (42)
C. carpioReduced growth (11,18), sluggishness, anorexia, convulsions, high mortality, reduced bone magnesium content (11), cataracts (18)
I. punctatusAnorexia, reduced growth, sluggishness, muscle flaccidity, high mortality, depressed Mg content in body and blood serum/bone (19)
A. japonicaAnorexia, reduced growth (20)
O. mykissReduced growth (21–24), anorexia (22–23), cataract(25), sluggishness, calcinosis of kidney (21–22), increased mortality, vertebral curvature, degeneration of muscle fibres and epithelial cells of pyloric caeca and gill filaments (23), reduced bone ash, Mg and elevated Ca content (24)
Poecilia reticulataReduced growth and feed efficiency, high mortality (43)
GeneralHypochromic microcytic anaemia (C. carpio-26, P. major-27, Salvelinus fontinalis-28, A. japonica-20)
Element/fish sp.Deficiency signs1
I. punctatusReduced growth and appetite, depressed bone Ca and Zn content, and serum Zn (29)
C. carpioReduced growth (18,30), cataracts (18), loss of appetite, high mortality, erosion of fins and skin, elevated tissue concentration of Fe and Cu in intestine and hepatopancreas (30)
O. mykissReduced growth (25,31–32,44), increased mortality (31–32), cataracts (25,31,44), short body dwarfism (25,44), fin erosion (31)
O. mossambicusReduced growth and appetite, loss of equilibrium, mortality (33)
C. carpioReduced growth (34,18), short body dwarfism, cataracts (18)
O. mykissCataracts (25,35), reduced growth, short body dwarfism (34,35), abnormal tail growth (34)
C. carpioReduced growth (34,18), cataracts (18)
S. salarIncreased mortality, muscular dystrophy, depressed glutathione peroxidase (enzyme) activity (36), reduced growth (37)
C. carpioReduced growth (18,38), cataracts (18), anaemia (38)
I. punctatusReduced growth (39)
SalmonidsThyroid hyperplasia (goitre, 40–41)

1 1-Ogino & Takeda (1976),
2-Yone & Toshima (1979),
3-Ogino et al. (1979),
4-Takeuchi & Nakazoe (1981),
5-Andrews, Murai & Campbell (1973),
6-Lovell & Li(1978),
7-Sakamoto & Yone (1980),
8-Sakamoto & Yone (1979),
9-Sakamoto &Yone (1978),
10-Arai, Nose & Kawatsu (1974),
11-Ogino & Chiou (1976),
12-Ogino & Takeda (1978),
13-Ketola (1975),
14-Lall & Bishop (1977),
15-Arai et al.(1975),
16-Arai, Nose & Hashimoto (1975),
17-Sakamoto & Yone (1973),
18-Satohet al. (1983),
19-Gatlin et al. (1982),
20-Nose & Arai (1979),
21-Cowey et al(1977),
22-Knox, Cowey & Adron (1981),
23-Ogino, Takashima & Chiou (1978),
24-Knox, Cowey & Adron (1983),
25-Satoh et al. (1983a),
26-Sakamoto & Yone(1978a),
27-Sakamoto & Yone (1978b),
28-Kawatsu (1972),
29-Gatlin & Wilson(1983),
30-Ogino & Yang (1979),
31-Ogino & Yang (1978),
32-Wekell, Shearer &Houle (1983),
33-Ishak & Dollar (1968),
34-Ogino & Yang (1980),
35-Yamamoto etal (1983),
36-Poston, Combs Leibovitz (1976),
37-Bell et al. (1987),
39-Gatlin & Wilson (1984),
40-Woodall & La Roche (1964),
42-Shearer (1988),
43-Shim & Ng (1988),
44-Satoh, Takeuchi & Watanabe(1987b)

Table 6. Reported dietary phosphorus availability (%) in selected fish1
Dietary sourceChannel catfishCommon carpRainbow trout
Sodium PO4, monobasic909498
Potassium PO4, mono-9498
Calcium PO4, monobasic949494
Calcium PO4, dibasic654671
Calcium PO4, tribasic-1364
White fishmeal-0–1866
Brown fishmeal-2474
Anchovy fishmeal40--
Menhaden fishmeal39--
Egg albumin71--
Brewers yeast-9391
Rice bran-2519
Wheat germ-5758
Wheat middlings28--
Corn, ground25--
Soybean meal, + hulls50--
Soybean meal, dehulled29–54--

1 Source: NRC (1983)

Table 7. Reported dietary mineral toxicity signs in fish
ElementFish speciesToxicity signs1
ZincC. carpioReduced growth (dietary level above 300mg/kg; 1)
Copperl. punctatusReduced growth (dietary level above 15mg/kg; 2)
SeleniumO. mykissReduced growth and feed efficiency, high mortality (dietary level above 13mg/kg (3,4), nephrocalcinosis (4,5)
  Reduced growth (dietary levels above 15mg/kg; 6)
 I. punctatus 
CadmiumO. mykiss/C. carpioScoliosis, hyperactivity, decreased bone calcium content (7– 10)
LeadO. mykissScoliosis, lordosis, black tail, anaemia, degeneration of caudal fin (11)
ChromiumO. mykissReduced growth and feed efficiency (12)

1 1-Jeng & Sun (1981),
2-Murai, Andrews & Smith (1981),
3-Hilton, Hodson & Slinger (1980),
4-Hicks, Hilton & Ferguson (1984),
5-Hilton & Hodson (1983),
6-Gatlin & Wilson (1984),
7-Koyama& Itazawa (1977),
8-Koyama & Itazawa (1977a),
9-Koyama & Itazawa (1979),
10-Roch & Maly(1979),
11-Johansson-Sjobeck & Larsson (1979), Tacon & Beveridge (1982)

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