Use of a feed additive to improve water quality, gut health, microbiota and fish performance in Atlantic salmon in recirculating aquaculture systems at higher temperature.
The goal of this trial is to study the effects of a feed additive on water quality management, gut health, gut microbiota and fish growth performance in high temperatures and gut health-challenged Atlantic salmon. Parts of the trial will be conducted with temperatures outside of the optimal temperature range of Atlantic salmon. This, coupled with necessary handling of the fish for weighing and sampling at the midpoint of the experiment, may cause moderate stress to the fish.
The use of recirculating aquaculture systems (RAS) allows for greater control over the quality of the water in which fish are cultured, including control over water temperature. However, in some areas where Atlantic salmon are raised in these systems, unseasonably warm weather can make it difficult to efficiently chill the water to the optimal temperature, which may result in reduced growth and potential health issues. One mechanism for this reduced growth may be interruption of the gut microbiota, or exacerbation of digestive system pathologies. In addition, reduction or removal of nitrogenous waste is a primary concern for the efficient management of these high density systems. Identification of compounds which can ameliorate the impact of these problems, and assessment of the incorporation of these into commercial fish feeds is an important step in ensuring the welfare of fish in RAS.
The proposed trial will require 840 Atlantic salmon, with a start weight of 300 grams. The number of fish is the minimum to maintain an appropriate density for observation of effects of the treatment on water quality parameters, and approaching a commercially relevant density, while allowing sampling at the mid-point of the experiment. The fish will be raised at a temperature within the optimal range of Atlantic salmon for six weeks before mid-point sampling, followed by a gradual increase of water temperature to a suboptimal level over a period of 3 weeks, before a final period of 4 weeks at this temperature.
It is anticipated that the fish may experience a slight reduction in appetite due to the suboptimal temperature, and mild to moderate gut irritation.
The use of recirculating aquaculture systems (RAS) allows for greater control over the quality of the water in which fish are cultured, including control over water temperature. However, in some areas where Atlantic salmon are raised in these systems, unseasonably warm weather can make it difficult to efficiently chill the water to the optimal temperature, which may result in reduced growth and potential health issues. One mechanism for this reduced growth may be interruption of the gut microbiota, or exacerbation of digestive system pathologies. In addition, reduction or removal of nitrogenous waste is a primary concern for the efficient management of these high density systems. Identification of compounds which can ameliorate the impact of these problems, and assessment of the incorporation of these into commercial fish feeds is an important step in ensuring the welfare of fish in RAS.
The proposed trial will require 840 Atlantic salmon, with a start weight of 300 grams. The number of fish is the minimum to maintain an appropriate density for observation of effects of the treatment on water quality parameters, and approaching a commercially relevant density, while allowing sampling at the mid-point of the experiment. The fish will be raised at a temperature within the optimal range of Atlantic salmon for six weeks before mid-point sampling, followed by a gradual increase of water temperature to a suboptimal level over a period of 3 weeks, before a final period of 4 weeks at this temperature.
It is anticipated that the fish may experience a slight reduction in appetite due to the suboptimal temperature, and mild to moderate gut irritation.
Begrunnelse for etterevalueringen
Forsøk som er betydelig belastende skal etterevalueres rutinemessig og forsøk med lavere belastningsgran KAN etterevalueres. Dette forsøket er klassifisert som moderat belastende og Mattilsynet har valgt at forsøket skal etterevalueres.
Etterevaluering
The experiment was moderately successful, generating useful data which may be used to optimise commercial Atlantic salmon RAS feeds. The fish group used may have been suboptimal, but data for further analysis was nonetheless able to be gathered.
600 Atlantic salmon were used in this experiment, with the severity of the effect of the treatments deemed to be moderate, as was applied for.
All efforts were made to minimise stress/treatment severity, within the constraints of the experiment. No improvements were identified which may further reduce the severity, without compromising the value of the data gathered.
600 Atlantic salmon were used in this experiment, with the severity of the effect of the treatments deemed to be moderate, as was applied for.
All efforts were made to minimise stress/treatment severity, within the constraints of the experiment. No improvements were identified which may further reduce the severity, without compromising the value of the data gathered.