Phytogenic feed additives (PFA) are plant derived products that are used in animal nutrition to improve feed/food quality, performance, and health status. However, knowledge regarding mode of action, competence to improve animal production, and aspects of application of PFA are limited. The aim of this thesis was to evaluate 18 plant derived test materials, by-products of the industry, and their water, ethanol, hexane extracts and fermented solid or liquid fractions, regarding their impact on various parameters of swine, especially weaners.
First the impact of the test materials on the caecal bacterial growth rate obtained from weaners was investigated using Hungate technique.
Further, the fermentations parameters (pH, redox-potential, SCFA, NH3, D- and L-lactate) were determined by supplementing the test materials to a semicontinuous in vitro flow system inoculated with caecum content of slaughtered finisher pigs. Additionaly, the properties of the test materials to interact in the adhesion of enterotoxigenic E. coli to the porcine intestinal epithelial cells IPEC-J2 were evaluated. Finally, various test materials were investigated in animal trials conducted with weaning pigs (two trials including four periods) regarding parameters of performance (weight gain, feed intake, feed conversion ratio, morbidity, and mortality), faeces (diarrhoea score, dry matter, and pH), haematology, differential blood count, phagocytosis (monocyte and granulocyte) and immunology (lymphocyte subsets CD4, CD8, CD21, and MHC-II).
It could be shown that PFA can have an influence on the bacterial growth rate depending on type and concentration of the test material. For example peels of Magifera indica L. had the highest inhibitory (basic raw material) and strong enhancing (water extract) effect on the growth rate (p<0.01). Furthermore, the type of the test materials can have an impact on caecal fermentation parameters. Water extracts lower the pH faster and stronger (p<0.01) and decreases the production of i-butyrate and i-valeriate (p<0.05) compared to basic raw materials. For example the addition of three different Vitis vinifera L. by-products reduced the ammonia concentration in the test system (min. p<0.05). It could be shown that the concentration and time protocol of test material and E.
coli addition to the IPEC-J2 adhesion assay can have a significant impact (p<0.01). The water extract of Thymus vulgaris L. reduced the attachment of E. coli to epithelial cells most effectively (min.
p<0.05). In frame of the animal trial no effects on the performance due to the test materials could be obtained. The basic raw materials of Salix alba L. and Sinupret® reduced diarrhoea. No further dietary related effects could be found. It has to be mentioned that the number of animals was limited in each trial. In frame of the thesis numberous correlations between the investigated parameters and the components of the test materials could be evaluated.
The findings point out that PFA can have siginificant impact on in vitro and limited impact on in vivo parameters and that the effects depend partly on the (pre-) treatment of the plant materials.
Further studies are necessary to characterise the composition of the test materials and their impact on mode of action, performance, and health status of pigs by suitable in vitro and in vivo methods.
Suggestions to improve the techniques used in frame of this thesis are provided.