Participating organizations (WP leader in bold): P7. IMR, P15. ULL, P17. NIFES and P20. SARC
Atlantic halibut larvae are approximately 12 mm in standard length (SL) at first-feeding and, because of their relatively large larval size, they are first-fed on Artemia. The main constrains for Atlantic halibut hatcheries are (1) slow growth during the late larval stages and (2) high mortalities caused by opportunistic bacteria and 3) slow growth after weaning.
Task 11.1 Early Weaning of Atlantic halibut. The activity in the present task will focus on manipulating the conditions of the larval environment in order to optimize feed intake, using Artemia cysts that we know are eaten by the larvae, as a reference particle. The experimental diets, one floating and one sinking, will be produced using the latest knowledge in diet formulation (SARC), including the best quality feed ingredients, a high level of phospholipids, easily digestibly protein and attractants.
Task 11.2 Development of a production strategy for on-grown Artemia. In the experiments on production of ongrown Artemia in Task 4.4.3, the nutrient profile of on-grown Artemia compared to Artemia nauplii will be characterized, both at the research facility and in the Atlantic halibut hatchery .
Task 11.3 Nutrient retention and digestive physiology of juveniles fed Artemia nauplii or on-grown Artemia. In the experiments in task 4.4.4, Atlantic halibut larvae will be fed Artemia nauplii from first-feeding . At 20 dpff one group of larvae will be transferred to on-grown Artemia whereas the other group will be continued on nauplii. The experiment will last until 70 dpff. In the present task, Atlantic halibut larvae from the experiment will be characterized with respect to digestive enzymes and ATPase activities. The on-grown Artemia will be nutritionally characterized and Atlantic halibut nutritional status (macro and micro nutrients) at different stages in development will be determined.
Task 11.4 Comparison of nutrient retention in Atlantic halibut larvae reared in RAS vs FTS. The study in task 4.4.1 aims to determine the potential effects changes of RAS vs FTS on gut flora and fish performance. One group of Atlantic halibut will be held in a flow through system while another group will be held in a RAS system. In the present task, analyses of digestive physiology (digestive enzymes and ATPase) will be performed and the nutritional profile of the larvae at 30 and 60 dpff will be measured in order to compare nutrient retention between the groups.
Task 11.5 Effect of dietary PL on digestion, absorption and metabolism of lipids in Atlantic halibut juveniles. Atlantic halibut juveniles (start weight approximately 1g) will be fed diets with increasing levels of PL (10-50% of total lipid) according to a regression design with 3 replicates and 5 levels, for two months. Growth, body indices, proximate composition of whole body and tissues will be monitored. Given that enough feces may be recovered from the halibut intestines, lipid digestion and absorption as well as the general uptake of nutrients will be described. Genetic markers will be used to describe how dietary PL influences the lipid metabolism, with focus on the intestine, including lipid digestive enzymes, enzymes involved in resynthesis of TAG and PL, remodeling of PL, synthesis of chylomicrons and export of lipids from the intestine.
Atlantic halibut larvae are approximately 12 mm in standard length (SL) at first-feeding and, because of their relatively large larval size, they are first-fed on Artemia. The main constrains for Atlantic halibut hatcheries are (1) slow growth during the late larval stages and (2) high mortalities caused by opportunistic bacteria and 3) slow growth after weaning.
Task 11.1 Early Weaning of Atlantic halibut. The activity in the present task will focus on manipulating the conditions of the larval environment in order to optimize feed intake, using Artemia cysts that we know are eaten by the larvae, as a reference particle. The experimental diets, one floating and one sinking, will be produced using the latest knowledge in diet formulation (SARC), including the best quality feed ingredients, a high level of phospholipids, easily digestibly protein and attractants.
Task 11.2 Development of a production strategy for on-grown Artemia. In the experiments on production of ongrown Artemia in Task 4.4.3, the nutrient profile of on-grown Artemia compared to Artemia nauplii will be characterized, both at the research facility and in the Atlantic halibut hatchery .
Task 11.3 Nutrient retention and digestive physiology of juveniles fed Artemia nauplii or on-grown Artemia. In the experiments in task 4.4.4, Atlantic halibut larvae will be fed Artemia nauplii from first-feeding . At 20 dpff one group of larvae will be transferred to on-grown Artemia whereas the other group will be continued on nauplii. The experiment will last until 70 dpff. In the present task, Atlantic halibut larvae from the experiment will be characterized with respect to digestive enzymes and ATPase activities. The on-grown Artemia will be nutritionally characterized and Atlantic halibut nutritional status (macro and micro nutrients) at different stages in development will be determined.
Task 11.4 Comparison of nutrient retention in Atlantic halibut larvae reared in RAS vs FTS. The study in task 4.4.1 aims to determine the potential effects changes of RAS vs FTS on gut flora and fish performance. One group of Atlantic halibut will be held in a flow through system while another group will be held in a RAS system. In the present task, analyses of digestive physiology (digestive enzymes and ATPase) will be performed and the nutritional profile of the larvae at 30 and 60 dpff will be measured in order to compare nutrient retention between the groups.
Task 11.5 Effect of dietary PL on digestion, absorption and metabolism of lipids in Atlantic halibut juveniles. Atlantic halibut juveniles (start weight approximately 1g) will be fed diets with increasing levels of PL (10-50% of total lipid) according to a regression design with 3 replicates and 5 levels, for two months. Growth, body indices, proximate composition of whole body and tissues will be monitored. Given that enough feces may be recovered from the halibut intestines, lipid digestion and absorption as well as the general uptake of nutrients will be described. Genetic markers will be used to describe how dietary PL influences the lipid metabolism, with focus on the intestine, including lipid digestive enzymes, enzymes involved in resynthesis of TAG and PL, remodeling of PL, synthesis of chylomicrons and export of lipids from the intestine.
