APPENDIX XV: TOXIC AND ANTI-METABOLITE SUBSTANCES OCCURRING IN FEEDS

The following table, which provides a summary of the toxic and anti-metabolite elements occurring in common feedstuffs which are known to affect aquaculture species, is extracted from New, (1986a):

Toxin or Antimetabolite

Type

Factor or Effect

Examples of sources

Fungal toxins

Aflatoxins

Produced by the mould Aspergillus spp., which grows, particularly in high temperature/high humidity conditions, on ingredients and compund feeds, particularly groundnut meals and cereals

T-2 toxins

As above, orginating from the mould, Fusarium spp.

Vomitoxin

Caused by Fusarium spp.

General deterioration of feed quality

Caused by Penicillium spp. moulds

Bacterial infection

Salmonella contamination

Contaminated ingredients, especially animal proteins, together with insects and rodent droppings

Mycobacteriosis

Unpasteurized trash fish and viscera

Bacterial toxins

Botulism

Trash fish stored anaerobically

Chemical contaminants

Pesticides and Herbicides, such as organo chlorine and poly chlorinated biphenyls (PCB's).

Plant ingredients, contaminated by spraying, and accumulation in fish and fish products used as ingredients

Heavy metals,e.g., Mercury

Concentrated by animals and plants used as ingredient sources

Various

Contamination of feeds by traces of chemicals used during feed processing e.g., lubricants, fumigants, water softening chemicals, etc.

Volatile N-nitrosamines (VNA)

Fish meal, especially that dried by hot air exhausted from an oil burner (direct heating/drying method)

Natural feed components

Cyclopropenoid acids Synergistic effect on aflatoxins and act as growth inhibitors.

Kapok and cottonseed oils

Cyanogenetic glycosides

Linamarin

In expeller linseed meals, lima beans, cassava

Dhurrin

From damaged or old sorghum and maize

Vitamin antagonists

Linatine (Anti-vitamin B₆)

Expeller linseed meals

Lipoxidase (Anti-vitamin A)

Soybean meal

Antivitamin D

Soybean meal

Antivitamin B₁. (Thiaminase)

An enzyme present in raw fish, particularly freshwater fish, herrings, mussels, clams, and shrimp

Antivitamin E

From kidney and haricot beans. (Note: vitamin E deficiency also caused by lipid rancidity)

Antibiotins (e.g., Avidin)

In raw egg white; normally egg (used in larval diets) is cooked. Biotin can also be inactivated by rancid fats

Alkaloids

Green parts of potato plants

Mimosine

Growth inhibitor from ipil-ipil (tangen-tangen)

Toxic amino acids

Chick peas

Natural feed components (continued)

Gossypol (reduces amino acid availability)

Pigment from cottonseed products

Glucosides

Rapeseed and mustard seed meals

Oxalic acid

Sugar beet

Phytates (from complexes with proteins, phosphorus, calcium, zinc, copper, magnesium, etc., thus reducing availability of these components)

Soybean, sesame, groundnut and cottonseed meals; cereal hulls, germ and endosperm

Protease inhibitors (affects activity of the trypsins and exacerbates sulphur-amino acid deficiencies)

Unheated or underheated soybean meal and protein concentrates

Haemagglutinins

Unheated soybean meal; various species of beans

Sapogenin glycosides

Soybean meal, alfalfa, sugar beet (not normally toxic but water extracts of some extracted saponins are used to kill fish during harvesting in some locations)

Peroxides

Oxidised oils

Poorly stored and inadequately protected (by antioxidants) ingredients, particularly those with high poly-unsaturated fatty acid levels such as fish oils and meals.

Toxin or Antimetabolite
Type	Factor or Effect	Examples of sources
Fungal toxins	Aflatoxins	Produced by the mould Aspergillus spp., which grows, particularly in high temperature/high humidity conditions, on ingredients and compund feeds, particularly groundnut meals and cereals
	T-2 toxins	As above, orginating from the mould, Fusarium spp.
	Vomitoxin	Caused by Fusarium spp.
	General deterioration of feed quality	Caused by Penicillium spp. moulds
Bacterial infection	Salmonella contamination	Contaminated ingredients, especially animal proteins, together with insects and rodent droppings
Bacterial infection	Mycobacteriosis	Unpasteurized trash fish and viscera
Bacterial toxins	Botulism	Trash fish stored anaerobically
Chemical contaminants	Pesticides and Herbicides, such as organo chlorine and poly chlorinated biphenyls (PCB's).	Plant ingredients, contaminated by spraying, and accumulation in fish and fish products used as ingredients
	Heavy metals,e.g., Mercury	Concentrated by animals and plants used as ingredient sources
	Various	Contamination of feeds by traces of chemicals used during feed processing e.g., lubricants, fumigants, water softening chemicals, etc.
	Volatile N-nitrosamines (VNA)	Fish meal, especially that dried by hot air exhausted from an oil burner (direct heating/drying method)
Natural feed components	Cyclopropenoid acids Synergistic effect on aflatoxins and act as growth inhibitors.	Kapok and cottonseed oils
	Cyanogenetic glycosides
	Linamarin	In expeller linseed meals, lima beans, cassava
	Dhurrin	From damaged or old sorghum and maize
	Vitamin antagonists
	Linatine (Anti-vitamin B₆)	Expeller linseed meals
	Lipoxidase (Anti-vitamin A)	Soybean meal
	Antivitamin D	Soybean meal
	Antivitamin B₁. (Thiaminase)	An enzyme present in raw fish, particularly freshwater fish, herrings, mussels, clams, and shrimp
	Antivitamin E	From kidney and haricot beans. (Note: vitamin E deficiency also caused by lipid rancidity)
	Antibiotins (e.g., Avidin)	In raw egg white; normally egg (used in larval diets) is cooked. Biotin can also be inactivated by rancid fats
	Alkaloids	Green parts of potato plants
	Mimosine	Growth inhibitor from ipil-ipil (tangen-tangen)
	Toxic amino acids	Chick peas

Natural feed components (continued)	Gossypol (reduces amino acid availability)	Pigment from cottonseed products
	Glucosides	Rapeseed and mustard seed meals
	Oxalic acid	Sugar beet
	Phytates (from complexes with proteins, phosphorus, calcium, zinc, copper, magnesium, etc., thus reducing availability of these components)	Soybean, sesame, groundnut and cottonseed meals; cereal hulls, germ and endosperm
	Protease inhibitors (affects activity of the trypsins and exacerbates sulphur-amino acid deficiencies)	Unheated or underheated soybean meal and protein concentrates
	Haemagglutinins	Unheated soybean meal; various species of beans
	Sapogenin glycosides	Soybean meal, alfalfa, sugar beet (not normally toxic but water extracts of some extracted saponins are used to kill fish during harvesting in some locations)
Peroxides	Oxidised oils	Poorly stored and inadequately protected (by antioxidants) ingredients, particularly those with high poly-unsaturated fatty acid levels such as fish oils and meals.