inter nationally-renowned Swiss company, pioneered the development of additives based on plant extracts, identified eugenol (from clove bud oil) and cinnamaldehyde (from cin- namon) for their specific properties with proven effect on ru- men fermentation. A decrease in the acetate/propionate ratio has been observed with animals fed a combination of these two active substances. This change leads to an effect similar to that of ionophores when it comes to volatile fatty acid pro- duction. Moreover, it had a significant effect on the inhibition of deamination, optimising the use of the degradable protein fraction by limiting ammonia losses.
Capsicum oleoresin (from red chili peppers) was also identi- fied for its beneficial properties. In beef cattle, it induces a change in dietary behavior by altering intake patterns, and increasing salivation. For animals supplemented with capsi- cum oleoresin, water intake is also higher. These effects are of particular interest in challenging situations such as heat stress. Numerous scientific publications have demonstrated the ability of plant extracts to strengthen animal perfor- mance. One displayed results of a meta-analysis in growth and feed efficiency on growing animals fed a mixture of eugenol, cinnamaldehyde and capsicum oleoresin (Bravo et al., 2009). This analysis showed consistent improvements in average daily gain (+2.8%) and efficiency (+2.6%). Furthermore, another study was conducted to determine the effectiveness of plant extracts containing capsicum oleoresin, cinnamaldehyde and eugenol as an alternative to monensin (Hagg et al., 2013). In this study, average daily weight gain was increased for animals fed plant extracts compared to those fed monensin (Table 1). Dry matter intake tended to be higher in the plant extract group, and overall performance expressed as feed conversion ratio was not affected. Integrity parameters were also recorded and the percentage of cattle
with a healthy rumen was improved when animals were supplemented with plant extracts.
Stability and standardization The selection and association of plant extracts requires many years of research. Beyond the selection of the components, the dose rate of each extract is decisive. To induce a physio- logical response, animals must receive precise blends of plant extracts at the accurate dosage for each component.
The term essential oils is often used when discussing plant extracts. Essential oils are obtained from the plant volatile fraction by steam distillation. However, for a defined plant, this volatile fraction can be highly variable. Crop conditions, variety and meteorology can all lead to qualitative and quan- titative differences in the composition of essential oils. When using plant extract compounds as feed additives, standardi- sation is therefore a key factor. The exact composition and concentration of active molecules must be known and trans- parent to ensure the correct dosage for each application. In the volatile fraction of plants, the most important active com- pounds are included in two chemical groups: terpenoids and phenylpropanoids. As these compounds are highly volatile, a technological process of encapsulation is then necessary to ensure the stability of the components in feeds.
Conclusion Plant extracts such as cinnamaldehyde, eugenol and capsi- cum oleoresin appear to be an effective alternative to AGPs in terms of animal performance. Supplementation of plant ex- tracts requires the use of a standardised and stable product with a transparent and specific composition. Dosage needs to be accurate and aligned with results from scientific studies in order to obtain the desired effect.
▶ ALL ABOUT FEED | Volume 28, No. 7, 2020 27
Plants extracts such as cinnamaldehyde, eugenol and capsi- cum oleoresin ap- pear to be an effec- tive alternative to AGPs in livestock.
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