Aquafeed Vol 14 Issue 3 2022

Page 53

PHYTOGENICS

Applications of phytogenics in shrimp farming Ruby Yu, Teresa M. Agulles Teixidó, PlusVet Animal Health

For the past two decades, the farming industry is moving towards a reduction in the use of antibiotics to prevent the emergence of antibiotic-resistant strains in humans. Feeds without antibiotic growth promoters (AGPs) are a reality in many countries, while others are looking into ways to restrict them. Different types of feed additives can be used to replace antimicrobial growth promoters, always combined with other types of interventions such as changes in feed formulation and improvements in biosafety and management practices. Since prehistoric times, humans have used plants to cure their own diseases and those of their animals. In the past 150 years, the use of medicinal plants has been shown to have a scientific basis: plants contain an abundance of chemicals, called “secondary compounds” or “phytochemicals”, that enable them to perform metabolic and ecological functions, such as resisting attacks by microorganisms and insects, and have been proved to exert useful health-promoting effects in human beings and animals. In the world of animal nutrition, plant derivatives are called “phytogenics” or “botanicals”. The group includes plant extracts, essential oils, purified natural compounds such as saponins, flavonoids, and tannins, and synthetic compounds that are identical to natural substances.

Mechanisms of action of phytogenics Since antibiotic growth promoters were banned in Europe in 2006, phytogenics have emerged as an effective alternative and their use is becoming widespread. When they began to be used on commercial farms, their mechanism of action was poorly understood, which made it difficult for nutritionists to include phytogenics in their feeds. However, in recent years, research work has multiplied,

and it has uncovered that the mechanism of action of plant derivatives as AGPs replacers is complex and multifunctional. Such complexity represents an advantage over other types of feed additives. Antimicrobial activity Many phytogenics are microbiocidal against Grampositive and Gram-negative bacteria, yeasts and fungi. As the microbiocidal activity of phytogenics arouses interest as substitutes for antibiotics, a multitude of research works has been carried out trying to determine their mechanism of action. It has been determined that their antibacterial activity takes place through different mechanisms: • Alteration of quorum sensing. When the number of bacteria within a population is large enough, each individual secretes and receives small signal molecules that allow the whole colony to act as a group. This communication system is called quorum sensing. Thanks to quorum sensing, bacterial colonies can form biofilms, become more virulent and secrete toxins, multiply faster and cross the intestinal barrier to enter the bloodstream. Since quorum sensing is responsible for pathogen virulence, finding active principles that can inhibit this communication system is a promising strategy to control pathogenic bacteria. Many phytogenics have been proven to disrupt bacterial quorum sensing at concentrations much lower than those needed to kill bacteria.

Aquafeed: Advances in Processing & Formulation Vol 14 Issue 3 2022


Turn static files into dynamic content formats.

Create a flipbook
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.