The evaluation of the nutritional potential of five Mediterranean woody plants rich in phytocompounds

Abstract

IntroductionShrubby vegetation is often the main feed resource for goats and sheep in dry areas. Nonetheless, successful integration of rangeland vegetation in livestock nutrition and the sustainable management of rangelands require appropriate characterization of the nutritive value of rangeland vegetation. Moreover, there is increasing interest in the use of natural compounds as alternative additives in ruminant feeding to improve the quality of meat and milk. Artemisia herba alba (ART), Eucalyptus globulus (EUC), Pistacia lentiscus (PIS), Rosmarinus officinalis (ROS) and Thymus capitatus (THY) are widespread in the Mediterranean area and used by the rural population for the extraction of essential oils (EOs), which represents an income-generating ABSTRACT. The foliage of woody plants, Artemisia herba alba (ART), Eucalyptus globulus (EUC), Pistacia lentiscus (PIS), Rosmarinus officinalis (ROS) and Thymus capitatus (THY), growing in central Tunisia was analysed for contents of nutrients and phytocompounds, including essential oils (EOs) and tannins. PIS and THY were highest in neutral detergent fibre and condensed tannins, respectively. EUC had the highest levels of total phenols, total tannins and oxalates. The concentration of EOs was highest in ROS and THY (26.59 ml · kg -1 dry matter (DM) vs 14.14 ml · kg -1 of DM, respectively). The EOs profiles differed among all the plant species. ROS and EUC EOs were composed mainly of 1,8-cineole (27.86% and 50.19%, respectively) while ART's EOs were dominated by camphor (16.28%) and chrysanthenone (14.78%). Carvacrol (44.24%) was the chemotype of THY EOs. The major compound of PIS EOs was α-pinene (12.82%). Biological assay showed that tannins affect the nutritive value of these plants. With the exception of THY, the association of polyethylene glycol to substrates incubated in calibrated syringes resulted in a major increase of gas production (+21% to +136%). Differences in the profiles of EOs extracted from the five woody species suggest that these EOs could differ in their impact on digestion and performance of ruminants. D. Aouadi et al. 161activity. These EOs, which are a volatile mixture of organic compounds obtained from plant material (flowers, seeds, leaves, fruits and roots) by physical means, are characterized by antibacterial, antiseptic and antioxidant properties (Derwich et al., 2011). In Tunisia, these medicinal and aromatic plants grow on native rangelands and most of them are browsed by sheep and goats. Extracts of these woody plants contain secondary compounds, such as EOs.Recent studies on ruminants showed that EOs extracted from range species could be used as natural additives to manipulate rumen fermentation and to improve feed efficiency (Benchaar et al., 2007). However, to our knowledge there is a lack of information on the presence of secondary compounds and the profiles of EOs in a wide range of Mediterranean woody plants. Therefore, the purpose of our study on the foliage of five tree and shrub species growing in central Tunisia was to dete...