Marine algae: evaluation of the potential for use in farm animal diets (review)

Currently, in the feed industry, along with energy-saving progressive technologies, non-traditional raw materials and secondary products of food industry are widely used. Processing and use of non-traditional resources at food enterprises significantly increases their profitability and reduces grain costs in compound feeds (P. Burtin, 2003). Natural components provide high-quality feeding for animals, strengthen their health and improve production performance. Currently, studies of the biological activity of algae phlorotanins are still relevant. The variety of biological properties determines their practical use, including in the production of feed additives for animals (S.B. Wang et al., 2013). An important problem is the uncontrolled use of antibacterial drugs, which can lead to the transfer of antibiotic resistance from animal to human (I.I. Kochish et al., 2019). Probiotics, prebiotics, symbiotics, organic acids, etc., serve as an alternative to feed antibiotics. These supplements are not inferior to antibiotics in effectiveness, but exclude their negative effects (I.A. Egorov et al., 2019). Seaweeds have a prebiotic effect due to the oligo- and polysaccharides and antimicrobial, immunomodulatory, antioxidant and anti-inflammatory activity due to bioactive compounds. Depending on the purpose of application and with the optimal dosage, seaweeds can positively affect animal ontogenesis, productivity and the quality of the products obtained. In poultry farming, seaweeds strengthen the immune state, reduce the microbial load in the digestive tract and improve product quality (A.M. Abudabos et al., 2012). Green algae ( Entermorpha prolifera ) contribute to better digestibility of nutrients, increase the level of metabolized energy, lead to higher egg production and a better egg quality (an increase in weight, shell thickness, change in yolk color), as well as reduce the yolk cholesterol level (S.B. Wang et al., 2013). Dried, boiled and autoclaved brown algae ( Sargassum dentifebium , Turbinaria conoides , Dictyota dentata , etc.) in the diet of young chickens and laying hens have no adverse effects on productivity performance and feed intake while positively influence yolk coloration and the calcium content in the shell. Dietary brown algae Sargassum sp. reduces levels of cholesterol and triglycerides in blood and yolk in laying hens with an increase in the yolk carotene, lutein and zeaxanthin concentrations (M.A. Al-Harthi et al., 2012). Red algae ( Asparagopsis taxiformis ) in the diet of animals can positively change the microbiome of the gastrointestinal tract, increasing the diversity and abundance of beneficial bacteria (B.M. Roque et al., 2019). Thus, due to its special biochemical composition, seaweeds is promising in feeding highly productive crosses of poultry, pigs and cattle.