Phytogenics: More than sensory additives

By Emmy Koeleman

Bioactive molecules derived from nature have already a long history in human medicine. Although these molecules (also referred to as botanicals, herbs or phytogenics) have a history of medicinal (and human food) use, there is little or no history in animal feed applications. In recent years, the ban of in-feed antibiotics, which was implemented in Europe in January 2006, has driven research activities regarding the potential of plant extracts and essential oils as alternatives to antibiotic growth promoters. The potential benefits such as increased feed intake, stimulation of digestion and improved feed efficiency among others have therefore raised the interest among animal nutritionists. However, it is not only in recent years that there were ideas around phytogenics in animal feed. In 1984 the first steps of developing phytogenic feed additives were made by Austrian company Delacon. Twenty five years later and backed up by many research papers and trials, phytogenics (plant extracts) are approaching a point where they are a standard ingredient in modern livestock diets. The immense data on this topic gathered over the last years were shared at the two day symposium in Greece, organised by Delacon.

Mode of action
Prof Dr Wilhelm Windisch from the University of Natural Resources and Applied Life Sciences in Vienna, Austria gave a clear summary on the current alternatives for antibiotic growth promoters. According to Windisch, essential oils from the labiatae plant family (e.g. thyme and oregano) are widely known to exert antimicrobial effects in vitro and several in vivo studies suggest that their overall impact on gut functions is similar to that of AGPs. “However, we still don’t know exactly if the antimicrobial activity of phytogenics is the real mode of action. Enhanced intestinal mucus production through bitter and/or hot substances is discussed as an alternative mode of action reducing the intestinal pathogen pressure in the animal.
  Regarding consumer safety Windisch said that it needs to be considered that many phytogenic principles are highly absorbable (e.g. essential oils). However, elimination of absorbed phytogenic substances seems to be quite efficient and therefore edible residues do not seem to pose a major concern to consumer safety.

Application in pig diets
Ken Purser from Value-Added Science & Technologies (VAST) in the US gave the audience a little insight in the use of Fresta F in pig diets. In the US, the product is primarily used in weaning diets and diets for lactating sows. Purser explained a large trial that was done to put the phytogenic product Fresta F to the test. It was shown that pigs with the phytogenic product gained 5.9% faster and 2.6% more efficient than the control pigs. It reduced the number of small pigs at 63 days with 39%. Jorge Marin, head nutritionist from Land O’Lakes in the US explained the use of a combination of a phytogenic (Fresta F) with a hydrating gel for pigs. “Water intake is very important and a reduced water intake leads to less feed intake and reduced performance” explained Marin. By providing a combination of a phytogenic product in combination with a gel, you get both the health stimulation effect of the plant extract and the hydrating effect of the gel. Marin explained that this type of product can be beneficial for light, heavy, sick, shipped and vaccinated pigs. Trials that were presented in the presentation showed that the product increased ADG and feed intake, improved gut health, reduced the pig weight variation and days to market.

Application in poultry diets
Dr Jan Dirk van der Klis from Schothorst Feed Research in the Netherlands talked about several challenges the European poultry market is facing or will be facing in the near future. He mentioned the EU welfare directive for broilers (to come into effect in 2010) and the EU welfare directive for layers (to come into effect in 2012). These new rules make maximum stocking density and NH3 output important criteria. “Animal nutritionists have therefore an important role in optimising poultry diets and improving the competitiveness of European poultry production despite these regulations,” said van der Klis. He also mentioned that since the EU ban on antimicrobial growth promoters (2006), the production of broilers and turkeys decreased due to an increase of intestinal disorders. Therefore, the level of dietary indigestible crude protein should be maximised to avoid protein fermentation in the intestinal tract. Particle size and insoluble dietary fibres are in turn valuable tools to improve intestinal health, Van der Klis addressed.

Effect on immune system
Prof. Dr. Jürgen Zentek from the Free University in Berlin, Germany gave an overview of the immune system in monogastric animals and the role nutrition can have to boost it. He addressed that the gastro intestinal tract of animal is the biggest immune organ and the barrier to the “outer world”. It has the purpose to uptake nutrients but also refuse pathogens from this outer world. “We can steer this to a certain extent by the choice of ingredients in the animal diets” according to Zentek. He specifically mentioned that the weaning period in pigs is a very stressful event, and in turn give a drop in immune responses. Nutritionists should be aware of this, and add specific immune boosting additives at this stage of the production cycle. Examples of these additives are plant extracts and beta-glucans. Stefanie Gärtner from the same University in Berlin presented her Ph.D.-work on the effect of Fresta F on the adhesion of pathogenic E. coli to porcine intestinal cells and on immunological parameters in piglets. The results from her in-vitro trials indicate an interference of the phytogenic feed additive with the adhesion of E. coli IPEC-J2 cells, she explained. The feeding trial showed some differences in the immunological traits between the trial and control group. “However, further studies should be done to explain the consequence for animal health” according to Gärtner.

Phytogenics and the environmental
Prof. Dr. Gerhard Flachowsky was highlighting that there is still a lot of work to do before an accurate calculation of the so called “Carbon footprints” can be used for regulations or restrictions. He was also pointing out that there is also a lot of “sun” in the rumen as undegradeable roughage can be transformed in high quality nutrients, and that this should never be forgotten even if there is the “shadow” of methane making a big portion of green house gas emissions caused by them. However emissions from livestock are already under legislative regulation. Carlos Piñeiro from PigCHAMP Pro-Europe in Spain pointed out some of the remedies to minimise the ammonia output from livestock production. Livestock produces 37% of the total global methane output, 65% of the total global N oxide and 64% of the total global ammonia output. “As a livestock industry we therefore have to take our responsibility to find solutions to bring these numbers down”, said Piñeiro. As possible solutions Piñeiro considered the reduction of crude protein in the diet – reducing 1 point crude protein can lead to an ammonia reduction of 60%, the implementation of phase feeding, the use of specific feed additives such as phytogenics to improve the utilisation of the raw protein and to reduce the urease activity.

Conclusion
From the amount of research work presented at the symposium we can certainly state that the interest (and the need) to use phytogenic feed additives is growing. The need to increase digestion, improve feed conversion, boost immunity and improve overall health through natural solutions is becoming more important in countries were in feed antibiotics are phased out or will be banned in the near future. However, more research is still needed to learn the exact mode of action of some known plant extracts, find new substances and increase our knowledge about the right application for different animal species.