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Advances in research on plant (essential oil) extracts in aquaculture
Plant extracts are composed of various bioactive compounds derived from plants, which have been traditionally used as fragrances, preservatives, and herbal remedies. Among these, essential oils represent the core component of plant-based extracts, consisting of aromatic and volatile substances. These oils are typically hydrophobic and contain a variety of chemical constituents such as alcohols, aldehydes, esters, ethers, ketones, phenols, and even some nitrogen-containing compounds. The six-carbon ring structure in many of these compounds contributes to their diverse biochemical properties, which can vary depending on the plant species and environmental conditions. As a result, plant extract-based feed additives are increasingly recognized for their safety, efficiency, stability, and controllability, making them a promising alternative in the green and sustainable animal feed industry.
Aquatic animals often encounter pathogenic microorganisms due to their feeding behaviors, and disease outbreaks can be complex, involving both pathogenic and non-pathogenic factors. While infections may be caused by viruses, bacteria, fungi, or parasites, other contributing factors include nutritional deficiencies, toxic substance accumulation, and poor water quality. This paper reviews existing research on plant-based feed additives, focusing on their antibacterial and antioxidant properties, as well as their mechanisms of action. It also highlights the impact of plant extracts on gut microbiota, nutrient digestion, and overall growth performance in aquatic species.
The growing concern over antibiotic use in animal production has led to stricter regulations, including the EU's ban on antibiotics as growth promoters since 2006. In the 1990s, synthetic drugs such as antibiotics, antifungals, and growth enhancers were widely used in livestock and aquaculture. However, rising antibiotic resistance and drug residues in food have prompted greater interest in natural alternatives like plant extracts. Studies have shown that excessive and improper use of antibiotics can lead to the rapid development of resistant bacterial strains, creating a critical situation where effective treatments become scarce.
The EU's stringent regulations on aquatic product safety could soon be adopted more broadly, significantly affecting countries that rely heavily on aquaculture exports. In 2007, representatives from Southeast Asian aquaculture industries signed a draft legislation proposing a strict ban on the use of human antibiotics in farmed animals, along with restrictions on veterinary drugs used as growth promoters.
One of the main active components in plant extracts is essential oil, which has been widely applied in animal feed to enhance immune function and improve health outcomes. The composition of essential oils varies depending on the plant source. For example, valerian essential oil contains thymol and carvacrol, which can make up between 3% and 60% of the total content. Similarly, essential oils extracted from Origanum vulgare ssp. hirtum contain over 30 different compounds, many of which are phenolic substances with distinct biological activities. These compounds have been shown to support gut health and maintain a balanced microbial environment in the digestive system.