Feeding fish on pellets is an important technology for aquaculture. To get better feeding results and reduce the cost of breeding rainbow trout, some tips should be paid attention to:
First, the shape, structure and size of the feed pellet not only affect the palatability, but also the digestibility, so you should choose the suitable feed pellets for fish at different stage. For feeding rainbow trout, feed pellets with particle size between 0.3mm and 2.2mm are suitable for fingerlings under 12g; particle size 2.2mm-3.2mm and length 3mm-4mm for fingerlings 12g-60g; particle size 3.5mm-4.5mm and length 4mm-5mm for fingerlings 60g-195g; particle size 5mm and length 6mm-8mm for fish above 195g. The suitable pellets can be swallowed completely and thus reduce the feed waste.
Second, dissolving oxygen amount in the water has an important effect on the intaking, digesting and growing of fish. Low dissolving oxygen content can lead to the poor appetite, low digestibility and slow growth of fish. The rainbow trout has vigorous metabolism, better growth and high efficiency of feed utilization when the dissolving oxygen content is above 9ml/L. While if the content is under 5ml/L, the respiratory rate of fish will speed up, under 4.3ml/L the fish will gasp for air and not take feed. For breeding rainbow trout, fish hypoxia generally happens in the back of pond, so the density in the back should be lower than the front, and sewage disposal should be in time to keep good water quality.
Third, different size and invasiveness of fish can have a negative influence on feeding in rainbow trout plant. In the breeding group, big fish with strong aggressivity will affect the appetite or feeding of small fish and then its growth. Before or during feeding, fish are very active and gathered, and the frequency of attacking each other is the highest. So you should increase feeding times or scatter the rainbow trout feed pellets evenly.
Forth, a proper feeding amount per day. A proper feeding amount is the key to high efficiency of feed utilization and low farming cost. With feed quotiety for feeding amount per day, that is, feeding amount depends on the percentage of feed dry weight accounting for the fish weight. At the rainbow trout fingerlings stage, the protein content of feed pellets is about 45%, then the percentage should be 3.7% when water temperature is 14°C and 4.3% when 16°C; for adult fish, the protein content of feed pellets is about 40%, then the percentage should be 1.8% when the water temperature is 14°Cand 2.1% when 16°C. The feeding amount calculated in this way can meet the nutrient requirement for normal growth of rainbow trout.
During rainbow trout breeding, we should adjust the pellets feeding amount according to the fish body weight gain.