Essential Oils in Livestock: From Health to Food Quality

Abstract

Using plant essential oils (EOs) contributes to the growing number of natural plants' applications in livestock. Scientific data supporting the efficacy of EOs as anti-inflammatory, antibacterial and antioxidant molecules accumulates over time; however, the cumulative evidence is not always sufficient. EOs antioxidant properties have been investigated mainly from human perspectives. Still, so far, our review is the first to combine the beneficial supporting properties of EOs in a One Health approach and as an animal product quality enhancer, opening new possibilities for their utilization in the livestock and nutrition sectors. We aim to compile the currently available data on the main anti-inflammatory effects of EOs, whether encapsulated or not, with a focus on mammary gland inflammation. We will also review the EOs' antioxidant activities when given in the diet or as a food preservative to counteract oxidative stress. We emphasize EOs' in vitro and in vivo ruminal microbiota and mechanisms of action to promote animal health and performance. Given the concept of DOHaD (Developmental Origin of Health and Diseases), supplementing animals with EOs in early life opens new perspectives in the nutrition sector. However, effective evaluation of the significant safety components is required before extending their use to livestock and veterinary medicine.

Keywords: antimicrobial; antioxidant; encapsulation; essential oils; fermentation; immunity; inflammation; livestock; mastitis; nutrition.

Figure 1

Distribution graph of the number of the articles containing essential oils (EOs) and a livestock animal or an animal food product according to the year of publication (2010–2021).

Figure 2

“Epic epoch” graph allowing to visualize the first 5 most used keywords in each article for each year, from 2010 to 2021.

Figure 3

Oxidation of terpenoids adapted from Reference [95].

Figure 4

Coacervation process adapted from Reference [105]. The bioactive molecule to be encapsulated (core) is first mixed with one polymer before adding the oppositely charged polymer. The complex coacervation process is generally spontaneous or induced by altering the physicochemical parameters (pH, temperature, ionic strength, etc.). This process leads to the formation of micrometric droplets (5–10 µm) with entrapped bioactive molecules. At the end, stabilization can be performed using chemical or physical treatments.

Figure 5

Essential oils in ruminant fermentation [216].

Figure 6

EOs in livestock from a One Health perspective. IL: Interleukin; NF-κB: Nuclear Factor Kappa B; TGF-β: Transforming growth factor-beta; IFN: Interferon; GPx: Glutathione peroxidase; SOD: superoxide dismutase; ROS: Reactive oxygen species, TBARS: Thiobarbituric acid-reactive species.