Fish oil is a small scleractinian fish or fish offcuts, the same as fish meal. The fish is pressed to release the fish oil, which is then further processed into fishmeal using steaming and drying techniques.
Fish oil is a source of energy, but most importantly, it provides the only source of long-chain omega-3 fatty acids, which are essential for fish and human health. Like humans, most fish cannot synthesize long-chain omega-3 fatty acids in their bodies, so they must obtain these fatty acids from food (for example, in the case of farmed fish, omega-3s come from fish oil from small scleractinian fish or from fish scraps in feed).
Fish meal is a high-protein ingredient made from the offal of small scleractinian fish or fish not commonly used for human consumption. It is used as a source of protein in feed. These ingredients come from countries such as Peru, Chile, Ecuador and Southeast Asian countries, and are imported into Australia.
Vitamins and minerals
Vitamins and minerals are added to the feeds to ensure that the fish obtain all the nutrients they require. These are the same vitamins and minerals as those used in supplements for humans.
Vegetable protein and oil ingredients
Plant ingredients such as wheat gluten, lupin flour and soybean protein concentrate are used as protein sources for feeds. Fish feeds aim to achieve a balanced amino acid composition and therefore use a mixture of plant proteins.
The inclusions of wheat and fava beans are sources of carbohydrates. Carbohydrates in the form of starch are broken down into sugars and used for energy, which is of limited nutritional value to predatory fish. Instead, carbohydrates are needed to help bind the pellets together in the manufacture of feed, making them stable and less likely to break down when they enter the water prior to consumption.
The durability of the feed pellets is also required to avoid any breakage or dusting of the feed as it is delivered to the fish through the mechanical feeding system, thus reducing the number of smaller feed pellets entering the water and reducing the chance of nutrients in the feed being released into the fish Watering the fish before they eat.
Land-animal protein and oil ingredients
Terrestrial ingredients used in Australia are sourced only from Australia and only from suppliers approved by the Australian Refining Association (ARA) and are AQIS export certified. They are also subject to our own supplier approval program and regular audits by Skretting representatives. The animals used are intended for human consumption; and are therefore subject to strict quality and food safety controls.
Terrestrial animal protein materials are high quality sources of protein; for example, poultry meal has a very similar amino acid composition to fish meal, making it a suitable substitute for fish meal in the feed of carnivores such as salmon and trout.
Astaxanthin is a naturally occurring carotenoid that wild salmon extract from the crustaceans they eat. This carotenoid is then deposited in muscle tissue and is delivered to the eggs of salmon during their reproductive cycle. Salmon cannot synthesize astaxanthin, so in aquaculture, natural astaxanthin is added to the feed.
Table 1. Alternate Sources of Protein that are Being Evaluated or have Potential as Partial or Whole Replacement for Fish Meal in Aquaculture Diets
|Soy meal||Poultry byproducts||Insect larvae|
|Rapeseed meal||Feather meal||Single cell protein|
|Sunflower meal||Shrimp and crab meal||Grasses|
|Oat groats||Blood flour||Leaf protein|
|Cottonseed meal||Fish silage||Vegetable silage|
|Wheat middlings||Meat meal||Zooplankton (krill, etc.)|
Protein (range), %
Table 2 Some Compounds Occurring in Feedstuffs that are Known and/or Suspected of Causing Physiological Abnormalities or Otherwise Impairing the Growth of Fish
|Glycosides||Grass and leaves|
|Phytates||All plant foods tuffs|
|Mycotoxins (aflatoxin)||Cereal-based meals not naturally occurring but produced by microorganisms|
|Cyclopropenoid fatty acids||Cottonseed oil and meal|
|Trypsin inhibitors||Soy and rapeseed meal|
|Mimosine||Leaves (Leucaena leucocephala)|
|Oxidized and polymerized lipids||Fish meal; poultry byproducts, krill meal|
|Histamine and putrescine||Fish meal, primarily tuna|