How to feed your fish?
Versele-Laga, which acquired Kronen Spezial-Tiernahrung, has amassed a wealth of experience over a good many years in the development and production of industrial fish food. Setting out from this experience and thanks to a solid collaboration of many years' standing with professional tropical fish and Koi breeders, a wide range of quality feeds has been put on the market under the Fishlix brand.
Production of the feed
In the production of fish food, a distinction is made between compression and extrusion. With compression technology, the feed mixture is partially compressed through so-called die blocks as a moderate temperature rise is added before being broken off at the required length. Because of their high density, these pellets sink very swiftly and dissolve equally rapidly. During extrusion, the food mixture is passed through the extruder (which looks very much like an oversized meat mincer) which, through the effect of the heat and pressure that are added, is bound into a mush before being cut at the required length by a rotating cutter located at the extruder head. This hydro-thermic process ensures that the starch inside the feed is broken down and dissolved, making it easy to digest whilst also giving extrudates a high level of stability which enables them to retain their shape for hours after they have been served out in the water. The introduction of extrusion as a food preparation techno-logy has made it possible to manufacture a range of floating feeds. Because of the wide number of benefits it offers, extrusion has become the leading manufacturing process for fish feeds with tropical fish breeders.
Purpose of feeding
The aim is to provide the organism with the nutritional components to fuel its needs. Nutritional components include proteins and minerals, such as calcium and phosphorus, required to build body tissue (e.g. muscle tissue and the skeleton). Nutritional fuels on the other hand are needed to maintain a variety of metabolic processes. The food used plays a major part in this, as it not only supplies the energy but also a whole host of other nutritional elements such as vitamins and micro-nutrients in support of the vital functions. Koi enthusiasts expect the feed they use to contain all required nutrients to be included in balanced proportion to enable the fish to grow and thrive, to support their general health and sense of well-being and to boost a clearly defined, coloring of the fish rich in contrast.
Fish differ from other pets. For one thing, fish are cold-blooded, which means that their body temperature is determined by the ambient temperature of the environment they dwell in. In terms of energy consumption, this is a good thing as no energy is required to maintain body temperature. This also means that the whole metabolism (and that includes the digestive processes) depends on ambient temperatures. This explains why fish living in full ground ponds take in next to no food during winter whilst feeding all the more as temperatures rise. A second feature of the fish metabolism is the fact that digested proteins which are present in the faecal residue are broken down into ammonium/ammonia. This means that protein use in fish is more efficient than it is in other animals who are only capable of breaking down proteins into urea. As water is exchanged in certain quantities, this may cause problems. This topic is treated more in-depth below.
Fish nutritional requirements
Fish feed first and foremost to keep up their energy levels. Offering a feed which has higher energy and improved digestibility requires the fish to feed less to take in the same amount of energy than they would with inferior quality feeds. Energy supplying fractions in the food are fats, proteins and carbohydrates. The gross energy content of these fractions, characterised by their calorie value, amounts to 40 megajoule for fat (rounded per kg), 24 megajoule for proteins and 18 megajoule for carbohydrates. In addition to their energy density, the digestibility of these fractions is another important element as non-digested organic substances are discharged with the faeces which prompts additional oxygen to be consumed in the water upon breakdown. Fat contains the highest level of digestible energy supplying fractions, followed by proteins and carbohydrates.
Protein requirements in fish
The praiseworthiness of any given feed is usually assessed in terms of its protein content. However, fish cannot lay claim to the complete protein content that is present in the mixture. Fish require amino acids (the materials that make up proteins). And they require the type of amino acids which they are unable to produce themselves (essential amino acids, such as lysine) which must therefore perforce be supplied through the feed they are given. Which explains why they require amino acids that serve as basic nutrients for the constitution and decomposition of proteins. What is far more important than the actual level of protein content in the feed are the digestibility and composition of the proteins in relation to amino acids. From a physiological standpoint, it makes sense to limit the protein content in such a way as to make sure that as little protein as possible is used as an energy carrier for the simple reason that the energy consumption of proteins causes the metabolism as well as the quality of the water the fish live in to be impacted in a negative sense. The accumulation of ammonium/ammonia in the water may lead to symptoms of poisoning.
In addition to the indirect effects of food composition on fish health (protein content, digestibility) there are a number of components which serve to directly impact this. Many illnesses in fish are secondary, i.e. they are only capable of developing when the organism is subjected to considerable stress, for example as a result of poor water quality or through human intervention (lack of oxygen or transport stress). Various studies have shown that vitamin preparations which were pre-mixed for this purpose, especially those containing higher vitamin C levels, are paramount when it comes to safeguarding immunity and the skin's regenerative powers. In this, the use of thermo-stable vitamin types is key, as only these types of vitamins are capable of withstanding the effects of temperature and pressure during the production of the feed.
The way in which fish are colored is prompted by pigments (colorants) in which carotenoids have a significant part to play. The latter are responsible for many of the sparkling yellow, red, blue and black hues. Whereas wildlife fish draw on nutrients - of either vegetable or animal origin - for their cartenoid supply, the same vibrant coloring can be achieved in pond fish by using a food containing the
right amount of carotenoids (e.g. betacarotene, astaxanthin, canthaxanthin).
The right food
With its Fishlix product line, Versele-Laga has devised a feed range that meets with the different requirements described above. For Koi carps for example, there is little need for a wide variety of foods as this particular fish food (available in 4 and 8 mm diameter pellets)
has been conceived as an All-In-One feed which can be fed throughout the year.
The renewed energy distribution with a balanced proportion between proteins and fats is easy on the metabolism of the fish and spares water quality whilst enabling the fish to swiftly stock up on energy reserves during spring and autumn.
The immunity promoting action of vitamin C compounded with betaglucans serves to stabilise the organism's capability to resist infection, making for improved remedying of stressful situations.
The combination of betacarotene and spirulina algae boosts the bright coloring of the fish.