Restrictions on the use of in-feed antibiotics in many countries has fueled interest in alternative products. One group of natural products known as phytogenics is being looked at as a potential replacement for antibiotics. Also referred to as phytobiotics or botanicals, phytogenics are plant-derived products used in feed to potentially improve pig performance. Aside from having antimicrobial activity, these products potentially provide antioxidative effects, enhance palatability, improve gut functions, or promote growth. However, research validating their potential benefits for pigs is somewhat limited.

According to a fact sheet from Kansas State University, phytogenics comprise a wide range of substances and thus have been further classified according to botanical origin, processing, and composition. Phytogenic feed additives include herbs, which are non-woody flowering plants known to have medicinal properties; spices, which are herbs with intensive smell or taste, commonly added to human food; essential oils, which are aromatic oily liquids derived from plant materials such as flowers, leaves, fruits, and roots; and oleoresins, which are extracts derived by non-aqueous solvents from plant material. Two of the most common phytogenic substances evaluated in swine include the spices oregano and thyme.

Pure plant-based phytogenics show multiple modes of action in animal nutrition because of their synergistic effects of the agents within a plant, compared to synthetic substances. The mode of action of most phytogenic feed additives is still not fully understood. However, here are some of the potential mechanisms by which they may improve performance.

Increased Feed Intake
The stimulatory effect of phytogenics on feed intake is due to the claimed improvement in palatability of the diet resulting from the enhanced flavor and odor, especially with the use of essential oils, KSU researchers said. However, the effect on feed intake of adding essential oils to pig diets is highly variable. Increased palatability of the diets associated with the addition of phytogenics also may be due to their anti-oxidative effects, which might contribute to preserving the desired organoleptic qualities of the diet.

Improved Gut Function
Improvement in gut function is mainly attributed to the possible stimulatory effect of phytogenic substances on digestive secretions, such as digestive enzymes, bile, and mucus. However, at the present time there is limited research in pigs exists to support this hypothesis, which is generally based on experiences derived from the use of spices in human nutrition. Phytogenic substances from certain herbs, spices, and their extracts have also been shown to have pharmacologic actions within the digestive tract, as evidenced by their relaxant and spasmolytic effects.

Anti-Oxidative Effects
Anti-oxidative properties of some phytogenic substances have been attributed to the phenolic terpenes in the essential oils. Essential oils of plants belonging to the Labiatae family have been widely used as antioxidants in human and pet foods with high fat content. However, whether they can be added in amounts sufficient to replace the effects of antioxidants commonly used in pig diets, such as ethoxyquin and butylated hydroxytoluene, remains to be seen.

Antimicrobial Effect.
The medicinal or antimicrobial properties of plant-derived substances have been well known for centuries. This property is mainly attributed to the essential oils of oregano and thyme, which contain the monoterpenes carvacrol and thymol, respectively. These oils have demonstrated high efficacy in vitro against several pathogens found in the intestinal tract. This suggests that phytogenic feed additives may be suitable replacements for in-feed antibiotics to improve pig health and growth performance. However, more research is needed to substantiate this information.

More evidence is needed to confirm the apparent beneficial effects on pig performance before these products are added to swine diets on a regular basis. Producers also should keep in mind that although these additives are considered “natural” products, they still need to be carefully evaluated for potential interactions with other ingredients or other potentially negative effects.

With increased awareness and control of antibiotic use, and further research on the properties and modes of action of these products, phytogenics may be a natural alternative for producers developing antibiotic-free feeding programs.