The pods and leaves of Acacia seyal are nutritious and palatable to livestock (Orwa et al., 2009). Leaves contain about 16% protein (11-20% DM, though higher values have been reported), 20-35% NDF and 12-25% ADF. Pods are richer in protein, with 15-24% in the DM (Feedipedia, 2011).
The smooth greenish-yellow bark, thick and soft when fresh, is extensively used for feeding livestock during the dry season, usually by cutting the tree to a height of about 1.5-2.5 m or by trimming off the thick branches so that the animals can browse the bark on the ground. Up to 5-6 kg/day is claimed to be sufficient for maintenance and even some milk production (Göhl, 1982). Bark contains less than 10% protein (Feedipedia, 2011).
The pods, leaves and flowers of Acacia seyal are palatable to livestock (Göhl, 1982). The level of astringent tannins should make it less palatable than other legume browse species such as Acacia nilotica and Sesbania sesban but the reverse was found, which was attributed to tannin loss during drying (Ebong, 1995).
Several studies have compared the preference of cattle, sheep and goats for Acacia seyal and other browse species in Sub-Saharan Africa. In the Sahelian zone of Burkina Faso, farmers considered shittimwood to be a major browse species for sheep and goats. However, tracking studies showed that sheep and goats browsed shittimwood much less than other species (notably Guiera senegalensis for sheep and Acacia senegal for goats) and that it was mostly browsed during the rainy and post-rainy seasons. Cattle browsed it less than sheep and goats (Sanon et al., 2007). A previous survey in Sahelian Burkina Faso showed than fodder trees, including Acacia seyal, represented a very small part of livestock diets (and particularly of cattle diets), even when there is little grass available during the dry season (Piot et al., 1980).
In Sahelian Cameroon, Acacia seyal leaves were one of the preferred feeds browsed by sheep and goats, and the preferred one during the rainy season (other preferred species were Acacia senegal, Pterocarpus lucens and Ziziphus mauritiana, which was the preferred browse during the post-rainy and dry seasons) (Ngwa et al., 2000).
Digestibility and degradability
Shittimwood was found to have a moderately degradable DM (52-55%) and one of the least degradable protein (40%) when compared to other browse species from natural pastures in Senegal (Fall Touré, 1991). Apparent N digestibility was 16.0-22.8% lower for teff (Eragrostis tef) straw-based diets supplemented with Acacia seyal than for diets supplemented with Acacia nilotica or Sesbania sesban. Rumen ammonia and N retention were also lower (Ebong, 1995). This lower N degradability or digestibility has been attributed to the high lignin and N-ADF (11% of total N) contents found in this species (Fall Touré, 1991), and to differences in types and levels of tannin and related polyphenols (Ebong, 1995).
Sheep and goats
In Uganda, supplementation of sheep and goat diets based on teff straw with Acacia seyal, Acacia nilotica and Sesbania sesban browse resulted in similar straw intakes for all supplements. Acacia seyal represented 37% of total DMI. Sheep consumed more Acacia seyal (+ 9%) than goats, and DM, OM and NDF digestibilities were lower in sheep, due to differences in retention times (Ebong, 1995).
In Ethiopia, supplementation of sheep diets based on teff straw with Acacia seyal leaves (40% of the diet) resulted in a growth of 10 g/d, comparable to that obtained with Sesbania sesban supplementation. Neutral detergent-soluble N in the faeces was highest for sheep fed Acacia seyal, indicating higher excretion of microbial and endogenous N in the faeces. Intake of Acacia seyal increased over time (Reed et al., 1990).