The chemical composition and potential nutritive value of the foliage of four subtropical tree species in southern Africa for ruminants

Abstract

The foliage of three Combretum species, C. apiculatum, C. molle and C. zeyheri, as well as that of Colophospermum mopane was collected over a period of two years. The chemical composition, in vitro organic matter digestibility (IVOMD) and the rumen degradability of dry matter (DM) and nitrogen (N) were determined on these samples. Mean values for crude protein (CP) concentration varied from 92 g/kg DM for C. molle to 141 mg/kg DM for C. mopane, the neutral detergent fibre concentration from 323 g/kg DM for C. apiculatum to 392 g/kg DM for C. molle and that of acid detergent fibre from 247 g/kg DM for C. apiculatum to 355 g/kg DM for C. molle. The calcium (Ca) concentration in the foliage was high (8-16 g/kg DM) compared to the phosphorus (P) concentrations of between 0.8-2.1 g/kg DM, resulting in an average Ca: P ratio of 9.3: 1. The foliage contained relatively low levels of sodium (Na), 0.041 g/kg DM, based on beef cattle standards. The IVOMD ranged from 53% for C. mopane to 64% C. apiculatum and the rumen degradability of DM from 78% for C. molle to 94% for C. apiculatum. The DM degradability was substantially higher than that of nitrogen, which varied between 47% for C. apiculatum and 60% for C. zeyheri. It was concluded that the foliage tested would not be suitable sources of N to supplement protein deficiencies in low quality herbage. Furthermore, browsers would require additional sources of P and Na to avoid deficiencies in these elements.


Keywords: Leaves, Combretum species, Mopane, Ruminal degradability, In vitro digestibility, Browse


South African Journal of Animal Science Vol.33(2) 2003: 132-141