Abstract:
Forage and browse legumes play an important role in sustaining livestock in small holder
farming systems in the tropics, mainly as a result of their contribution to economic and
environmental sustainability of livestock production. The study was conducted to determine the
chemical composition, ruminal degradability and in vitro digestibility of dry matter (DM) and
crude protein (CP) of Dichrostachys cinerea and Bauhinia thonningii leaves. The browse tree
leaves were harvested in the wild in Shayandima, Limpopo province. The leaves were collected,
oven-dried, milled to pass through a 1.0 mm sieve and analysed for chemical composition in the
Animal Science Nutrition Laboratory, at the University of Venda. The browse tree leaves were
analysed for DM nitrogen, neutral detergent fibre (NDF) and acid detergent fibre (ADF).
Approximately 5 g of leaf sample milled to pass through through a 1 mm sieve were placed in
nylon bags (external dimension: 6 × 12 cm, pore size of 41 μm) and incubated in duplicates for
0, 4, 8, 16, 24, 48, 72, 96 and 120 hours periods in the rumen of three cannulated Bonsmara
steers. The residues were then analysed for DM and nitrogen. Parameters to describe the
dynamics of ruminal degradability of DM and CP were obtained by fitting the data on the
exponential equation P = a + b (1 - e-ct) using NEWAY computer program, where “a” is the rapid
degradable fraction, “b” is the slow degradable fraction and “c” is the outflow rate. The in vitro
DM and CP degradability of rumen undegradable residue collected after 24 and 48 hour
incubation was determined by sequential in vitro digestion in pepsin (abomasal) and pancreatin
(small intestine) solutions. DM and CP content differed significantly (P ˂ 0.05). D. cinerea
leaves had higher levels of DM and CP content than B. thonningii leaves. DM and CP
disappearance increased (P < 0.01) as the incubation period increased. There was no
difference (P > 0.05) in soluble fraction ‘a’ and ‘b’ of DM of the two species. The CP
components for both fraction ‘a’ and ‘b’ differed significantly (P < 0.01) for CP among the two
species. There was significant difference (P < 0.01) in post-ruminal digestibility among the two
species. CP digestibility of B. thonningii and D. cinerea leaves was reduced (P < 0.01). In
conclusion, B. thonningii and D. cinerea leaves showed significant difference based on their
fermentation kinetics and in vitro digestibility, suggesting a good nutritional quality which can be
used as protein source for ruminants in dry season and supplement to low-quality diets.
