Understanding Phytogenics

Phytogenics exert pronounced flavoring properties, hence having an impact on the palatability of commercial diets. Moreover, their secondary metabolites, such as bitter or pungent substances, saponins, essential oils, alkaloids or flavonoids, are considered the plants’ secrets holders. The effects and economic impact of PFAs under commercial conditions, where consistent improvements in feed intake, growth rate and feed conversion were reported, confirm positive results from an ever growing number of scientific publications.

In fact, the effectiveness of plant active ingredients has often been underestimated in recent years and not seldom their mode of action is misunderstood even by companies offering such products. It is often postulated that PFAs are antimicrobial. In deed many secondary plant ingredients and extracts do have such properties. The in vitro antimicrobial activity of plant active ingredients is well documented through scientific findings and plants themselves can respond to bacterial or viral attack for example by producing 'phytoalexins'. However, it would be inappropriate to limit the value of phytogenic substances to an antimicrobial effect only. The complexity of plant secondary metabolites has far more to offer: Stimulation of saliva and gastric juices, support of liver function, anti-inflammatory and anti-oxidant effects are among those properties that are highly important for in vivo efficacy of PFAs, as recent research shows.

Formulating Phytogenic Feed Additives

The fine art of formulating PFAs lies in a suitable combination of the right plant materials. This requires a deep understanding of the flavoring properties, as well as the biological effects of plant compounds in the animal organism. Only the combination of different plant materials, including, for example, herbs and spices in complete and finely ground form, essential oils and nonvolatile extracts allows for making use of the full potential that plants offer. An interaction of all constituents working harmoniously together makes a well-formulated PFA more potent than the sum of its individual parts. In this context, PFAs must be clearly distinguished from products based solely on nature-identical compounds.

The Importance of Flavour

A very important property of PFAs is their influence on feed flavor, particularly in young animals. Perception of flavor is a complex physiological response. It is a combination of taste, which stimulates receptors in the mouth, and odour or aroma, which stimulates receptors in the nasal cavity. To be perceived as aroma, molecules must be volatile but both volatile and non-volatile molecules may have a taste. There are several types of flavor which can be added to feed to enhance or mask the natural flavor characteristics of feed and thus improve palatability. However, there are differences between animal species. The susceptibility to taste, for example, differs depending on the number of taste buds (Table 1).

Versatile Mode of Action

Phytogenic compounds have a versatile mode of action, which had been a big myth for those who used these substances as additives in animal feed. Therefore, a major objective of research and development in the last few years was to understand the role of PFAs in improving animal performance (Hippenstiehl et al., 2011; Windisch et al., 2008). However, the vast number of phytogenic compounds and the differences in composition of PFAs makes it impossible to postulate a general mode of action that is applicable to all commercial PFAs in the market.

Improving Digestibility – Optimizing Efficiency

Recently, more scientific data was generated, which enables us to put the right blocks together and understand better how our phytogenic additives contribute to productivity in animal production. An improvement in digestibility is a main effect ultimately leading to better growth performance and feed efficiency. Such improvements were reported for proximate nutrients and amino acids in pigs (Maenner et al., 2011; Figure 1) and poultry (Mountzouris et al., 2011).

Figure 1. Digestarom® increases ileal digestibility (meta-analysis of two trials with weaning piglets; Maenner et al., 2011)

Improved digestibility is a consequence of different effects:

• stimulated gastric and intestinal secretions
• optimisation of the intestinal microbiota
• reduction of microbial toxic metabolites in the intestine
• relief from immune stress, including a reduction in sub-clinical intestinal inflammation processes

Phytogenics Inhibit Cellular Inflammation

Recent scientific work points out that a potent anti-inflammatory efficacy plays a major role in the mode of action of Digestarom. Experts in livestock production are aware of the importance of controlling subclinical intestinal inflammation processes in the herd or flock because of the losses that occur due to this incidence. As such, anti-inflammatory effects of Digestarom can largely contribute to animal performance. In order to understand how Digestarom exerts its anti-inflammatory effect, we had to dig very deeply at sub-cellular level to elucidate the exact mechanisms involved.

In an experiment carried out at the University of Giessen (Germany), the anti-inflammatory activity of Digestarom was examined in a test model with inflammation-induced intestinal cells. The inflammation was induced by treating the cells with tumor necrosis factor a (TNFa). These cells were incubated or not with an extract of Digestarom. The first element to study was the nuclear factor kB (NF-kB). This is a protein complex and a very important transcriptional factor that controls the expression of different genes [interleukin 8 (IL-8), intracellular adhesion molecule (ICAM-1) and monocyte chemotactic protein (MCT- 1)] that are involved in the regulation of the pro-inflammatory response. The experiment revealed excellent inhibitory effects of Digestarom on IL-8, ICAM-1 and MCT-1 (Figure 2). Thus, Digestarom exerted a highly positive effect on the cellular inflammatory status by down regulation of NF-kB.

Figure 2. Intestinal protection: Anti-inflammatory effect of Digestarom (down-regulation of NF-kB target genes)
*Significant difference vs. induced inflammation (Control + TNF a) (P<0.05)

Another very important cellular element is the transcription factor Nrf-2, which is responsible for anti-oxidative activity. Activation of the Nrf-2 pathway leads to the induction of genes responsible for cellular defense against reactive oxygen species and detoxification of xenobiotics. Nrf-2 is located in the cytoplasm in a protein complex. Digestarom was found to up-regulate Nrf-2 target genes, i.e. cytochrome P450 isoform1A1 (CYP1A1), heme oxygenase-1 (HO-1) and UDP glucurono-syltransferase isoform 1A1 (UGT1A1) (Figure 3).

Figure 3. Intestinal protection: Anti-oxidative effect of Digestarom (up-regulation of Nrf-2 target genes)
*Significant difference vs. control (P<0.05)

Regular supplementation of Digestarom in the diet acts as a prophylactic against inflammatory reactions in the gastrointestinal tract by inhibiting the NF-kB factor and stimulating the anti-oxidative factor Nrf-2. This activity interrupts the damaging circle of the release of inflammatory mediators that otherwise would provoke intensive inflammation and the resulting necrosis and performance depression (Syed, 2011).

September 2012