How to manage the feeding
It is possible to have poor results even with good feed if the feed is not used correctly. Feeds should be thought as ordinary consumer goods that have manufacturer's recommendations and instructions for use. From the manufacturer's point of view, the failure to follow the instructions is like driving a car without engine oil even though the manual states all the related risks. The end user of the product always carries the final responsibility of the feeding levels.
Results from biomass, not from pieces
Both feed and fish density greatly affect your farming results. The initial density should be defined so that fish still have enough space in the pools at the end of production. When you're selling, it is about kilos rather than pieces of fish and so, too many fish in the pool is not a good option since it restricts the growth.
- Less than 20 kg per cubic meter has proven to be suitable density for the end stage of rainbow trout farming, taking each farm's conditions into account. Even in good circumstances, it has been noticed that as the density exceeds 20 kg, dorsal fin injuries increase considerably. The fish density in the most Finnish farms is 17 kg per cubic meter, says Olle Lerche, Raisioagro's R&D Manager in fish feeds who also has a strong background in fish farming.
Over the past few years, many farmers have noticed well above 10% differences in growth and feed coefficients between different pools. They first thought the reason for this was to be found in the feeds. However, after closer examination, it was noted that the final quantities between the pools were different. The differences may result from initial weighing but the major reason, especially in the sea environment, has been the "invisible" fish mortality. At some point, probably during the first sea summer, some fish, very commonly even 10-30%, have died unnoticed by the farmer.
The correct fish density is directly linked to the oxygen conditions in the pools. To function properly, current feeds require good oxygen conditions in the pool. Too high fish density lowers the oxygen concentration weakening the feed and increasing fish death. The placement of pools in a row also increases the decline in oxygen concentration in the pools.
Each feeding or visit at the pool area is stressful to the fish as the movement at the pools triggers the "food's coming" reaction and the competition for food begins. For larger fish of over 500 grams, one feeding in 24 hours is enough. At Raisioagro, we call it a once-a-day feeding model.
Modern growth feed contains a large amount of energy, and fish need to have time to digest it. If the daily dose is given all at once, the fish have 24 hours to digest the nutrition, which guarantees that most of the feed is used by the fish. After the feeding, oxygen consumption and thus also the demand for oxygen are at their highest. Therefore, the feeding should be scheduled to match the best oxygen time of the day.
Feed portion given at one feeding has been proven to affect the uniformity of fish schools. By giving the food all at the same time, the feeding period gets longer. According to the pecking order, the strongest fish get to feed first. When the once-a-day feeding is continued for a longer time, the fish at the lowest level of pecking order will also have feed.
Use feeding tables
Constant overdosing of feed, in the hope of bigger fish, has backfired on many farmers. We have developed our feeding tables, or recommendations for the use of our feeds, for over 20 years. They have proven to be very accurate and the exceeding of recommended amounts is often a conscious risk.
To read more about the feeding tables, click this link.