Phytogenic compounds in ruminant nutrition

Phytogenic, plant-based, products have gained increased interest with the passage of the Veterinary Feed Directive (VFD) and a general increase in customer resistance to the feeding of antibiotics to livestock.

Bryan Miller

Phytogenic products are the result of distillation and concentration of compounds found in commonly-known herbs and plants. As such, many discount the potential efficacy of products as being “voodoo science.” In reality, many medicinal compounds we are familiar with today came from natural sources. Perhaps the best known is penicillin. Additionally, commercial products have concentrated the efficacious compounds, which would be unavailable from the consumption of the raw foodstuffs.

In their concentrated forms, these active ingredients can have profound activities in a number of areas including anti-microbial, anti-inflammatory, anti-oxidant and others, depending on compound.

One of the difficulties with new technologies is the realization that not all phytogenic products are formulated the same, nor is the quality of the raw ingredients the same. Distillation processes can have different efficiencies in concentrating key compounds, and differing raw ingredients may have differing concentration of these same compounds. It is important that any product have a strong quality-control (QC) program behind it to ensure both consistency and efficacy.

Understanding goals

Given the wide variety of actions from phytogenic compounds, it is important to know what effects are expected in determining opportunities for improved animal performance. With ruminant nutrition, there are two major considerations: (1) how do products affect rumen fermentation through selection of bacterial species; perhaps stimulating some and decreasing others and (2) How do the products affect lower-gut health in terms of both integrity and efficiency.

Cattle production has come under pressure for concerns regarding the production of greenhouse gases. Much effort has gone into developing phytogenic products that can reduce methane generation and increase propionate-to-acetate ratios.

Positive goals, but there can also be negative consequences. Sometimes there is a concomitant decrease in microbial protein that can result in both less and a poorer amino acid balance reaching the abomasum. To date, there have been both successes and failures, and more work needs to be put into fine-tuning products or identifying appropriate rumen conditions for use.

Having, or not having, a rumen effect does not preclude significant effects in the lower gut. There is published work showing phytogenic compounds having significant rumen bypass. In fact, many phytogenic compounds may have greater bypass value than “conventionally calculated.” Many phytogenic compounds exhibit their anti-microbial activity by entering the microbial cell wall and increasing permeability to hydrogen ions entering the cell. As these cells also pass down the GI tract, they are digested and the active phytogenic compounds may be rereleased where they can have an active effect in the lower gut.

Alternatives to antibiotics

Phytogenic products have been proposed as a potential replacement or supplement to antibiotics fed as growth-promotants. Along these lines, it must be remembered that antibiotic effects on growth are as much or mostly due to their anti-inflammatory actions rather than their anti-microbial actions. As such, phytogenic products are well-positioned to be effective feed additives. Thymol and eugenol are well documented to exhibit anti-inflammatory effects in other species.

In addition to their potential to replace or supplement antibiotics, phytogenic compounds may actually potentiate or increase the effectiveness of antibiotics. In vitro studies have shown that both antibiotics and phytogenic compounds may have similar anti-microbial properties against specific compounds, but combining the products has a much greater effect than either product separately.

Could we reduce either or both the amount and the amount of time antibiotics are fed? Could this improve our ability to reduce specific pathogens known to cause specific problems such as F. necrophorum associated with liver abscesses common to feedlot cattle?

Anti-inflammatory uses

Perhaps the greatest effects of phytogenics are their anti-inflammatory and anti-oxidant properties. By reducing the inflammatory cost and oxidant cost typically associated with the digestive tract, even without clinical problems, phytogenic products can improve an animal’s ability to produce growth by freeing up nutrients, in particular energy and amino acids.

Gut integrity is an area of animal health that continues to receive additional interest and study. Gut integrity and the prevention of “leaky gut” can have a profound effect on animal performance. With leaky gut, you have the potential for proteins to enter the lumen of the intestine, resulting in a “bloom” of pathogenic bacteria such as clostridia, which can in turn produce toxins, adding injury to the digestive tract. With leaky gut, the cells in the villi must expend more energy to absorb nutrients, resulting in reduced efficiency.

Additionally, leaky gut can allow greater absorption of pathogenic bacteria, lipopolysaccharides (LPS) and toxins including mycotoxins in the feed. Absorption of these compounds can also result in fevers and reduced feed intake, both of which negatively affect production. Direct evidence in cattle is limited as such experiments can be difficult and expensive; however, work in other species indicate the key phytogenics can assist in reducing the effect of leaky gut.

Leaky gut is also part of the problem cattle encounter with heat stress. Phytogenic products have the potential to assist in cattle undergoing heat stress. From a direct standpoint, capsicum has been used to help cattle keep cooler by increasing vasodilation.

However, other phytogenic products may work through reducing heat stress by reducing the leaky gut issue. Through two completely different modes of action, phytogenic products have the potential to reduce heat stress in cattle.

PHOTO: Studies into phytogenic products are opening possibilities on efficiencies related to emissions, anti-microbial usage, anti-inflammatory usage and heat stress. Staff photo.