Application of manures and other fertilizers, as well as the excess use of feeds may reduce the quality of pond water. In the case of pond culture of common carp, the combined use of natural fish food and supplementary or/and balanced feeds is a technique which promotes both a good pond environment and improved fish nutrition.
Besides a wide range of natural food, common carp readily feeds on grains and pelleted feeds (Table 5.2). Supplementary feeds (Table 5.3, Table 5.4 and Table 5.5) can be grains and by-products, but also include compounded farm-made or commercial feeds (Table 6.1 and Table 7). A common characteristic of such supplementary feeds is that none of them, when used alone, ensures a biologically fully balanced (shortly balanced) diet for common carp. With these types of feeds, consumption of natural fish food in certain proportions is still needed. Otherwise fish will not grow properly. This is because all the nutritional requirements of carp are not covered by them; essential proteins, minerals and vitamins are missing from such feeds. Consequently, they must be obtained from the natural food produced in the pond.
The role of natural fish food in a pond reduces as intensity of production increases. Parallel to the intensity of common carp production, the importance of feeding also increases. At extensive and semi-intensive production, cheaper, energy-rich feeds are used to supplement the protein-rich natural food. Together with the increase in intensity of production, a better and more complete diet is needed. A good practice is to mix the application of supplementary and balanced feeds to carp when the standing biomass increases. In the mixture, either the proportions of protein-rich supplementary feeds are increased or the different grains (wheat, maize, sorghum, etc.) are supplemented with compounded pelleted feeds. The proportion of compounded feed in the mixture increases parallel to the standing crop of common carp (Figure 10 and Figure 11; Table 8.1).
In intensive tank and cage-culture systems of common carp, all nutritional requirements (protein, energy, minerals and vitamins) should be exclusively covered by the applied balanced feed in order to ensure healthy development and growth of fish.
Supplementary feeds
The contents of supplementary feeds distributed in a pond (Figure 12) are presented in Table 5.3, Table 5.4 and Table 5.5. Supplementary feeds with diverse energy and protein content have different food conversion ratio (FCR) (Table 5.2). These absolute values of FCR are gained if the listed feeds are fed as a mono-diet alone (i.e. without natural fish food). If supplementary feeds are fed in fish ponds, their FCR will be less. This reduced value of FCR is relative to and depends upon many factors, including:
- climatic and weather conditions;
- quantity and quality of natural fish food;
- daily frequency of feeding;
- ratio of energy and protein-rich supplementary feeds given to fish;
- age of carp and size of their standing stock;
- combination of different large cyprinids;
- biomass of unwanted feed competitors, such as small cyprinids or other feed and/or natural food-consuming fish species; and
- number and type of feed-competing water birds.
Under typical fish-pond conditions, the measured FCR of supplementary feeds will also change in the course of production seasons. Accordingly, it is more favourable in the first period when natural food is in abundance, and worsens later, as the standing stock of carp increases and the quantity of accessible natural fish food declines. Relative values of FCR of grains for the entire season of extensive or semi-intensive production of one-summer-old, two-summer-old and table fish should be about 1–2, 1.5–2.5 and 2–3.5 (Table 5.2) (Woynarovich, Moth-Poulsen and Péteri, 2010).
In Central and Eastern Europe, traditional pond feeding of carp takes place once a day, five days a week, which certainly cannot exploit the growth capacity of the fish. This is why daily feeding is essential. Feeding the same daily ration in two or three portions can improve FCR significantly (Hancz, 1982). The recommended daily maximum quantity of supplementary feeds changes according to the size of the fish, as demonstrated in Figure 13.
Formulated feeds
There are two types of formulated feed which are used in carp culture:
- compounded, often pelleted, farm-made or industrial feeds used in the pond culture of common carp; their protein content varies between 20 and 35 percent, while their components and ratio within the diet depend on the actual standing biomass of common carp (Table 6.1) and
- fully balanced feeds to be used in tanks and cages (Table 6.2); their protein content varies between 35 and 55 percent.
Fully balanced feeds (Table 6.2) are compiled to be used in tank and cage-fish culture systems. These feeds are developed to fulfil all nutritional requirements of different size/age groups of common carp from larvae to broodstock. Their crude protein content changes from 35 to 55 percent and they contain mineral and vitamin premixes, as well as antioxidant.
