FUNCTIONAL FEED ADDITIVES TO PREVENT FISH PARASITES

Aquaculture is expected to continue to expand and fulfill the increasing global needs for fish and shellfish. But as the industry grows and intensifies its production systems, biological plagues are becoming more critical factors affecting profitability of aquaculture producers. All commercial aquaculture species such as salmon, shrimp, marine fish, tilapia and pangasius suffer from a variety of parasites which often cause important economic losses. Gill and skin flukes are causing increasing problems in fish farms, such as Sparycotyle crisophrii in Mediterranean seabream Sparus aurata, or Gyrodactilids in tilapia worldwide. A wide diversity of protozoan ectoparasites infests freshwater fish, including white spot, Trichodina spp,… Endo-parasites such as digenean worms, acanthocephalan, to coccidians, mixosporidians, and microsporidians (Eimeria spp, Enteromyxuum spp) attack the digestive system and internal organs. The traditional approach to combat fish parasites, based on the use of chemicals and some therapeutics once the parasite outbreak is detected, is increasingly hampered by the development of resistance and the increasing restrictions on the use of chemicals. Health promoting feed additives are a crucial component of effective disease prevention strategies and have already become a standard ingredient in premium brands of salmon feeds designed to reduce the impact of sea lice. A wide range of additives with different mode of actions are currently offered including yeast extracts, phytobiotics, probiotics, prebiotics, organic acids and their derivates. Functional feeds containing gut health promotors deliver with every meal an adequate concentration of natural compounds which can work through multiple mechanisms to reduce the success of the parasitic infestation. Natural compounds with anti-parasitic activity can work directly on gut parasites or reach the blood and/or mucus to affect ecto-parasites, whereas immune modulators can change the composition and thickness of the mucus.

This presentation will review the latest advances in the research and development of health promoting feed additives, both in laboratory and field conditions, showing their efficacy to boost fish health and reduce the economic impact of parasites on fish production. A number of case studies will be presented, including the prevention of gill flukes and endoparasites in Gilthead seabream Sparus aurata and European seabass Dicentrarchus labrax.