Do indigenous browse trees influence chemical composition and in vitro dry matter digestibility of parasitic plants?

Abstract

This study examined the influence of nine browse trees on the chemical composition and in vitro dry matter (DM) digestibility (IVDMD) of parasitic plants (Tapinanthus lugardii, Erianthenum ngamicum, Viscum rotundifolium and Viscum verrucosum) found in Botswana. Browse trees did not have any effect (P>0.05) on chemical composition and IVDMD of T. lugardii. Acid detergent fibre (ADF) in E. ngamicum was highest (P<0.05) in samples harvested from Acacia fleckii (340.2±13.1 g/kg DM) and was lowest (266.4±32.1 g/kg DM) from those harvested from Acacia tortilis. V. verrucosum parasiting either A. tortilis or Dichrostacys cinerea had higher (P<0.05) levels of crude protein (CP) (177.9±9.4 and 172.7±9.4 g/kg DM, respectively) than those parasiting Acacia robusta (140.6±9.4 g/kg DM). Concentrations of calcium in V. verrucosum harvested from A. robusta were higher (P<0.01; 20.6±1.4 g/kg DM) than that from either A. tortilis (14.2±1.4 g/kg DM) or D. cinerea (14.0±1.4 g/kg DM). Phosphorous level of V. verrucosum was higher (P<0.01) in samples from A. tortilis versus those from A. robusta and D. cinerea (2.1±0.2 versus 1.3±0.2 g/kg DM versus 1.3±0.2 g/kg DM, respectively). Levels of CP of V. rotundifolium were higher (P<0.001; 195.8±10.5 g/kg DM) from samples from Boscia albitrunca and lowest (114.4±10.5 g/kg DM) from those harvested from Maytenus senegalensis. V. rotundifolium parasiting Ziziphus mucronata had the highest (P<0.05) phosphorous levels (2.0±0.1 g/kg DM) while that from B. albitrunca and M. senegalensis had the lowest concentrations (1.6±0.1 and 1.5±0.1 g/kg DM, respectively). Crude protein (182.6±4.6 g/kg DM versus 161.3±4.1 g/kg DM), calcium (Ca) (21.8±0.7 g/kg DM versus 16.5±0.7 g/kg DM) and neutral detergent insoluble nitrogen (NDIN) (11.5±0.5 g/kg DM versus 7.5±0.4 g/kg DM) were higher in browse trees than in parasitic plants. Plotting CP, Ca, P and IVDMD against months of January to June showed that nutrient contents of parasitic plants closely follow those of their host browse trees. There was a month effect for IVDMD, neutral detergent fibre (NDF), acid detergent lignin (ADL) (P<0.05) and calcium (Ca) (P<0.001), but not for acid detergent fibre (ADF), phosphorus (P), CP and NDIN (P>0.05) within the parasitic plants. Browse trees appear to have some effect on the nutritive value of some parasitic plants. The parasitic plants with their associated browse trees may provide an alternative supply of nutrients to livestock when these are in short supply from natural forages.