EFFECT OF SUPPLEMENTING TEFF STRAW WITH DIFFERENT LEVELS OF LEUCAENA OR SESBANIA LEAVES ON THE DEGRADABILITIES OF TEFF STRAW, SESBANIA, LEUCAENA, TAGASASTE AND VERNONIA AND ON CERTAIN RUMEN AND BLOOD METABOLITES IN ETHIOPIAN MENZ SHEEP

In vitro gas production, dry matter and nitrogen degradabilities of fr esh and sun-dried foliages of four fodder trees (FTs) (Sesbania sesban , Leucaena leucocephala, Chamaecytisus palmensis (tagasaste), Vernonia amygdalina) and of teff straw were estimated. In Experiment 1, feed s amples were incubated in three different rumen environments (ecologies ) created by feeding sheep the following: teff straw, teff straw + 174 g dry matter (DM) of sesbania and teff straw + 167 g DM of leucaena. In Experiment 2, different rumen ecologies were created by feeding tef f straw supplemented with 119, 178 or 232 g DM day-1 of sesbania or wi th 117, 175 or 232 g DM day-1 of leucaena. Gas production constants we re estimated following the equation: GP =B(1-e(-Ct)) where GP is gas p roduced at time t, B is potential gas production and C is the rate of gas production at time t. Rumen fluid was sampled at 3, 6, 9, 12 and 2 4 h after feeding in Experiment 2 and pH, NH3-N, volatile fatty acids (VFAs) and minerals determined. Plasma urea nitrogen (PUN) concentrati ons were estimated in blood taken from the sheep at 3, 6, 9 and 12 h. Drying relatively increased the neutral detergent fibre (NDF), acid de tergent fibre (ADF) and NDF-nitrogen concentrations in all foliages ex cept in leucaena. Dry sesbania, tagasaste and vernonia had lower nitro gen concentrations than the fresh ones but the opposite trend was obse rved for leucaena. Dry matter disappearance (DD) at incubation times o f 3-48 h and degradation constants differed among the four foliages (P < 0.05). Compared with the other foliages, sesbania had lower fibre f ractions and degraded faster. Drying of foliages reduced degradability . Supplementation did not affect (P < 0.05) the DD of fresh foliages b ut enhanced (P <0.05) the rate of dry foliages. There was not feed typ e x rumen ecology interaction (P>0.05) for either dry or fresh foliage s. The rate of teff straw degradation in sheep fed supplemented diets was increased (P<0.06). Gas production was lower in dry than in fresh foliage. Gas production values (ml per 200 mg DM) for dry foliages wer e: sesbania, 55.5; tagasaste, 54.5; vernonia, 49.5; leucaena, 45. Corr esponding values for fresh foliages were: tagasaste, 81.8; sesbania, 6 2.7; leucaena, 51.1; vernonia, 51. The rates of gas production (h-1) w ere highest for dry tagasaste (0.0779), followed by sesbania (0.0718), leucaena (0.0563) and vernonia (0.0477). Corresponding values for fre sh foliages were: leucaena, 0.0541; tagasaste, 0.0528; sesbania, 0.047 8; vernonia, 0.0366. Supplementation increased levels of all rumen met abolites measured. Rumen NH3-N was highly correlated (r = 0.88; P < 0. 05) with PUN. Correlations among the other metabolites were either low or negative. The results are discussed in relation to the chemical co mposition, type and form of fodder tree and the rumen ecology resultin g from feeding these foliages.