Dietary Inclusion of Woody Species Leaves: Dose-Dependent Effects of Secondary Metabolites on In Vitro Ruminal Fermentation Parameters

Abstract

In the context of sustainable livestock systems, native forage resources from drylands are gaining attention for their nutritional and functional properties. In semiarid regions, woody species are vital for livestock nutrition during the dry season, offering bioactive compounds like condensed tannins. This study evaluated native woody species of Argentinean Dry Chaco for their nutritional potential in ruminant feeding. Selected species included Schinopsis balansae Engl., Prosopis alba Griseb., Acacia aroma Gillies ex Hook. & Arn., Libidibia paraguariensis (D. Parodi) G.P. Lewis, Cercidium praecox (Ruiz & Pav.), Larrea divaricata Cav., Ziziphus mistol Griseb., and Prosopis nigra (Griseb.) Hieron. Plant leaves exhibited varying levels of crude protein, fiber, and phenolic compounds, with P. nigra showing the highest protein content and L. paraguariensis having the highest phenolic content. In vitro tests revealed that higher leaf inclusion reduced gas production, indicating slower fermentation. L. divaricata and L. paraguariensis had the highest digestibility, while ammonia nitrogen and total volatile fatty acid production decreased, enhancing fermentation efficiency. A 12.5% leaf inclusion optimized digestion, highlighting these species’ potential as sustainable forage for silvopastoral systems, benefiting livestock nutrition and environmental sustainability.