Evaluation of chemical composition and in sacco ruminal degradation characteristics of leaves and fruits of condensed tannin rich tree species

Abstract

The objectives of this study were to determine the chemical composition, in sacco rumen dry matter and organic matter degradability of leaves and fruits of indigenous tannin rich multipurpose tree species (MPTS) and also to assess the relationship between chemical composition and in sacco ruminal degradability parameters. The MPTs studied were Ekebergia capenesis, Ficus sycomorus, Maesa lanceolata and Rhus glutinosa. The leaves and fruits of the MPTS were collected from the Omo-Nada woreda of Jimma zone, southwestern Ethiopia during East African Autumn season. Chemical composition measured were dry matter (DM), crude protein (CP), crude ash (CA), ether extract (EE), crude fiber (CF), neutral detergent fiber (NDF), non-fiber carbohydrates (NFC) and condensed tannin (CT). In situ rumen degradability was measured with of three rumen fistulated Holstein Friesian-Boran cross steers in times at 0, 6, 12, 24, 48, 72 and 96 h. Ruminal in sacco OM degradabilities were estimated from residues in nylon bags. The DM and OM degradability data were fitted to the exponential equation Y = a + b (1 – e–ct). The values for each chemical constituents was ranged from 92.43 to 96.84% DM, 5.43 to 11.49 % CA, 7.97 to 17.06 % CP, 1.57 to 31% EE, 12.20 to 27.5% CF, 5.84 to 39.30 %NFC, and 7.2 to 16.72% CT. For DM degradation, the highest and lowest values of soluble fraction (a) of leaves were recorded in M. lanceolata (14.55% DM) and E.capensis (-16.20% DM), respectively (P<0.001). The highest (0.12%/h)in E.capensis leave and lowest (0.01%/h) for R.glutinosa leave were the values of degradation rate(c). However in OM degradation kinetics, the ‘a’ value was ranged from -1.02% in R.glutinosa to 10.69% in E.capensis leaves where the variation was significant for the plant species (P<0.001); on the other hand, the highest and lowest ‘a’ value was recorded for fruits of R. glutinosa (31.84%) and E.capensis (14.22%) (P<0.001). The insoluble but degradable fraction (b) was 83.35% in R. glutinosa and 45.21% in E.capensis leaves (P<0.001); On the contrary, the highest and lowest values of potential degradability (PD) was recorded for F.sycomorus (89.89%) and 55.90% for E.capensis leaves (P<0.001). On the other hand, the highest and lowest effective degradability(ED) value was obtained in R.glutinosa (63.97%) and E. capensis leaves (P<0.001). The degradation rate constants (c) varied widely between MPTS with similar rates for E.capensis and F.sycomorus leaves. In general, it was observed that variation of plant parts lead to highly significant differences in DM and OM degradability and the degradable parameters. DM and OM degradation were highly correlated with time taken for the incubation, CP, NFC and CT concentration. The edible parts of MPTS recorded more than 60% DM and OM degradability at 24 h, which implied that they were all highly degradable in the rumen. Their incorporation into ruminant feeding systems as dry season forage supplements is therefore highly recommended.