by Dr Robert Tillner, Product Manager, Aller Aqua Group
Farming fish in increasingly sophisticated Recirculating Aquaculture Systems (RAS) has gained popularity across the globe. Whether RAS are built from scratch or existing fish farms have converted to RAS technology – fish produced in RAS represent a steadily growing volume of the total aquaculture production volume.
Farming fish in increasingly sophisticated Recirculating Aquaculture Systems (RAS) has gained popularity across the globe. Whether RAS are built from scratch or existing fish farms have converted to RAS technology – fish produced in RAS represent a steadily growing volume of the total aquaculture production volume.
One of the reasons is that the control measures in RAS technology allow for fish production under constant environmental conditions. This accurate optimisation between water parameters and fish biomass requires external factors to seamlessly integrate into this equilibrium. In this respect, feed is the most influential external factor in RAS and needs to provide the following benefits from a farmers’ point of view:
• High feed efficiency
• Optimal water quality
• High fish growth
Consequently, feeds for RAS need to target the specific requirements of this highly sophisticated and complex production technology by taking the following features to a new level:
• Nutrient digestibility and palatability
• Faeces quality
• Fish metabolism and DP:DE ratio
• Technical quality of the feed
• Feed functionality
Nutrient digestibility and palatability
In RAS, feeds with high nutrient density can unleash their full potential if the nutrients are readily available for fish metabolism and growth. The gross energy level is therefore not a useful indicator as nutrients get lost via faecal excretion.
In contrast, the digestible nutrient content of raw
materials indicates the nutrients retained in the fish body after
non-digestible energy has been lost in the faeces. Thus, assessing nutrient
digestibility of each raw material is the groundwork for any feed of stable
quality. Nevertheless, for accurate determination of nutrient digestibility the
following obstacles need to be considered:
• Raw materials differ in nutrient composition: obviously, fish meal and wheat differ in nutrient composition. But fish meal also varies in composition between different types of fish meal as well as within the same type. These differences in nutrient composition within a raw material need to be accounted for in the same way as between different raw materials like fish meal and wheat. This is required to provide the necessary accuracy when determining the nutrient digestibility of each raw material.
• Raw materials differ in nutrient digestibility: the nutrients from raw materials vary in digestibility. This is due to the nature of each raw material as well as the processing conditions and processing grade. Consequently, raw materials need to be evaluated in accordance to exact origin and season. This means that determining the nutrient digestibility of each raw material just once is not enough because of seasonal variations of raw materials as well as changes in processing conditions.
• Raw materials differ in nutrient composition: obviously, fish meal and wheat differ in nutrient composition. But fish meal also varies in composition between different types of fish meal as well as within the same type. These differences in nutrient composition within a raw material need to be accounted for in the same way as between different raw materials like fish meal and wheat. This is required to provide the necessary accuracy when determining the nutrient digestibility of each raw material.
• Raw materials differ in nutrient digestibility: the nutrients from raw materials vary in digestibility. This is due to the nature of each raw material as well as the processing conditions and processing grade. Consequently, raw materials need to be evaluated in accordance to exact origin and season. This means that determining the nutrient digestibility of each raw material just once is not enough because of seasonal variations of raw materials as well as changes in processing conditions.
Read more HERE.
The Aquaculturists
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