Despite the current global challenges, the aquaculture sector has shown significant growth over the last few years. In 2020 a growth of 2.7% in volume was observed, which elevated the total volume of aquaculture, excluding algae, to 87.5 million metric tonnes. The expectation is, that in 2021 or 2022, the aquaculture volumes will have surpassed the capture fisheries volume, which was recorded at 90.3 million metric tonnes in 2020. One of the main drivers of these growth numbers is the intensification of aquaculture production. Growth rates and feed efficiency have been improved, whilst at the same time stocking densities have been increasing over the past years. Besides increased productivity, this also resulted in increased disease pressure. Over the past decades, diseases emerged globally, which disrupted production chains and led to enormous economic losses. The first response to this increased disease pressure was the massive use of antibiotics. However, the use of antibiotics is shown to be harmful to animals and the environment. Next to that, it is shown as unhealthy for humans since accumulation of antibiotics in animals might lead to health issues and/or bacterial resistance. Since the acknowledgement of the need for reduction of an-tibiotics, the industry and the academic world has been focusing on new solutions to increase fish and shrimp resilience, for example by using feed addi-tives. The general hypothesis is, that when animal health and resilience are increased, the need for antibiotics will be reduced. In this article, several feed additives will be addressed on how they can help in the mission to reduce antibiotic use in aquaculture.
Selenium is an important nutrient in animal production as it plays a vital role in the antioxidant defense of humans, livestock, fish and shrimp. Especially during stressful periods, for example during handling or diseases, this trace element will support the animal by contributing to the reduction of reactive oxygen species (ROS). The importance of selenium is widely known, but the consumption by aquatic animals of selenium is under pressure. Usually selenium is present in high concentrations in marine-based ingredients, yet with the increased use of plant-based ingredients in aquafeed, the amount of selenium in the fish and shrimp diets has been decreasing. The decreased levels of selenium in the diet accompanied by the increased disease pressure highlights the importance of adding additional selenium to the feed. The addition of selenium in the organic form of L-selenomethionine is shown to be a good option, since selenium in this form can be stored in animal tissues. This allows for the best results, since it ensures a constant selenium supply by safe deposits of selenium that can thereafter be used by the animal during times of stress or when selenium uptake is limited. One example of this is a trial done in Thailand by Dr Wangkahart et al. (2022).