Chemical composition and in vitro dry matter digestibility of four parasitic plants (Tapinanthus lugardii, Erianthenum ngamicum, Viscum rotundifolium and Viscum verrucosum) in Botswana

Abstract

Parasitic plants, Tapinanthus lugardii, Erianthenum ngamicum, Viscum rotundifolium and V. verrucosum were harvested during months (January, March, May and June) in 1998 at the Sebele Research Station. The samples were separated into leaves and stems, (first 15–20 cm of shoots) or used as whole plants and analysed for crude protein (CP), acid detergent fibre (ADF), acid detergent lignin (ADL) and minerals. In vitro dry matter digestibility (IVDMD) was determined. There was a significant (p<0.05) month and species effect on CP. The month effect assumed a linear (p<0.01) response. The CP increased from the first month (January) of sampling to a maximum at the last month (June) of sampling and ranged from 104 to 206 g/kg DM. Although the month effect was not significant (p>0.05) on minerals, Cu increased in a linear (p<0.05) fashion from the first month to the last month of sampling, while the reverse was true for Ca. The species V. rotundifolium had significantly (p<0.01) higher CP than E. ngamicum (163 vs. 125 g/kg DM). There were significant species influences on Cu (p<0.05) and Zn (p<0.01). V. rotundifolium had higher Cu and Zn than the other species. Crude protein (182, 125, and 98 g/kg DM), ADF (208, 332 and 402 g/kg DM), IVDMD (59.1, 41.3 and 33.8% DM), Fe (205, 112 and 95 ppm) differed significantly (p<0.01) between leaves, whole plant and stems of E. ngamicum. There were also significant (p<0.05) differences between leaves, whole plant and stems of E. ngamicum for Ca, Mn, Zn and ADL, except Cu and P. Higher levels of Ca, Mn and Zn were found in the leaves than in the stems, while the converse was true for ADL. Plant fractions of T. lugardii differed significantly for ADF (219, 265 and 357 g/kg DM; p<0.01), ADL (91, 107 and 150 g/kg DM; p<0.05), IVDMD (48.8, 46.7 and 34.6%; p<0.01), and Zn (20, 21.8 and 30.3 ppm; p<0.05) in the leaves, whole plant and stems respectively. Crude protein, Ca, P, Cu, Fe and Mn were not significantly (p>0.05) different among the plant fractions of. T. lugardii. For the species T. lugardii and E. ngamicum, the stems had high content of fibre and lignin but low IVDMD. Although there was variation in chemical composition among the species and months, the levels of nutrients were constantly higher than what is expected in natural grasses, especially during the dry season. This suggests that these parasitic plants can be effectively used as nutrient