Preference and In Vitro Digestibility of Leaves of Woody Plants by Sheep in the Northern Sudanian Zone

In West Africa, trees and shrubs are important for feeding ruminant livestock during the dry season. This study aimed to determine the in vitro digestibility of organic matter from eight woody species using a gas test with and without the addition of polyethylene glycol (PEG), and evaluate their preference by sheep using a cafeteria test. Plants cited by farmers as being palatable to sheep were Lannea microcarpa (La), Ficus sycomorus (Fi), Pterocarpus erinaceus (Pt), Khaya senegalensis (Kh), Azadirachta indica (Az), Bombax costatum (Bo), Guiera senegalensis (Gu) and Ziziphus mauritiana (Zi). For the preference test, two groups of fresh and dried leaves from each time four species were offered in a 4 × 4 Latin square to four 18-24-month-old rams for 8 days each. The in vitro organic matter digestibility (IVOMD) was determined using the modified Hohenheim gas test. The quantity of dry matter ingested within 30 min, along with consumption time, ingestion rate, and the preference coefficient, served as indicators of leaf preference. Bo, Kh, and Zi leaves had the highest preference coefficients both in the dried (0.7, 0.3 and 0.2) and fresh (0.7, 0.5 and 0.3) state. Fresh Fi leaves had a higher preference coefficient (0.4) than dried ones (0.1), while the reverse was observed for Pt leaves (fresh: 0.1, dried: 0.6). PEG addition increased IVODM and in vitro methane production of ligneous forage plants by 1.2% (Kh) to 44.7% (La) compared to the incubation without PEG. In conclusion, fresh and dried leaves of B. costatum, K. senegalensis, and Z. mauritiana are highly palatable to sheep, making them good candidates for inclusion in dry season rations, despite their moderate IVOMD. In contrast, L. microcarpa and G. senegalensis exhibit both low preference and poor IVOMD, rendering them less recommendable as forage resources.