Nutraceutical Potential of the Low Deciduous Forest to Improve Small Ruminant Nutrition and Health: A Systematic Review

Nutraceuticals are defined as livestock feeds that combine their nutritional value with their beneficial effects on animal health. We analyzed the outcomes from nearly 20 years of research assessing the nutraceutical properties of plants consumed by sheep and goats in low deciduous forests. A systematic review of different databases suggested 31 peer-reviewed manuscripts according to pre-established criteria. Amongst these, 16 manuscripts described in vitro evaluations investigating the bioactivity of plant secondary compounds in the extracts of 12 plant species. Most of these studies used the abomasal nematode Haemonchus contortus as the parasite model. Meanwhile, 11 manuscripts reported in vivo trials under controlled pen conditions, evaluating the relationships between the intake of leaves from different plant species and their secondary compounds and animal nutrition, performance, and gastrointestinal nematode infections. Additionally, four manuscripts described studies under natural feeding conditions. Altogether, the studies showed the inherent complexity of the relationship between small ruminants, plants, nutrients, secondary compounds, and gastrointestinal nematodes in natural feeding systems. Several plant species can be considered good candidates for nutraceutical use. Our findings warrant future work to understand the relationship between plants, ruminants, and their parasites, with the aim to improve the sustainability of production systems based on the native vegetation of tropical forests.