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Two experiments were conducted to investigate the effect of supplementation with fodder tree leaves on the utilization of teff straw. This ivas aimed at testing the hypothesis that forage supplements (e.g. sesbania) that disappear faster from the rumen compared with those that disappear slowly (eg. leucaena) may elicit higher intakes of the basal diet. Experiment 1 investigated the effect of level (i.e. 0,200,300 and 400 g/kg dry matter (DM) intake) of leaves of Sesbania sesban or Leucaena leucocephala on the utilization of teff straw fed ad libitum. Seven sheep were given the seven diets in four periods following a partially balanced (7 × 4) cross-over design. In experiment 2, teff straw alone or supplemented with graded levels of sesbania (250, 350 and 450 g/kg DM intake), were fed to 16 sheep in a completely randomized block design. Intake, degradability, nitrogen (N) utilization, particulate and liquid passage rates were estimated.In experiment 1, protein source × protein level interaction was not significant. Supplementation increased intakes of total DM (P < 0-05), organic matter (P < 0·01) and N retention (P < 0·01) but had no effect on the intake of teff straw. Supplementation with sesbania, but not with leucaena, increased (P < 0·05) the apparent digestibility of DM. Both supplements increased (P < 0·05) the fractional rate of passage from the rumen. In experiment 2, graded levels of sesbania increased DM intake (P < 0·05), fractional rate of liquid outflow (P< 0·05) and tended to increase the rate of degradation. It was concluded that the effect of fodder tree leaves on roughage intake is a function of their disappearance rate from the rumen.

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The disappearance of dry matter (DM), nitrogen and cell wall constituents of the pods of Leucaena leucocephaia and some Acacia species incubated in the rumen of Jersey cattle was studied. The chemical compositions of the pods (seeds husks), seeds and husks were examined separately. Amino acid and lipid analyses were limited to the pods and seeds, while mineral and tannin analyses were done on the pods alone. The seeds had higher crude protein (CP) contents than the pods, with values ranging from 200 to 300 g CP kg À1 DM. The Leucaena pods and seeds had higher (p > 0.001) CP contents than the Acacia pods and seeds. The neutral detergent ®bre concentrations in the husks were higher than in the pods and seeds with the pods of A erioloba having the highest and those of A nilotica the lowest values. These values were highly in¯uenced by the seed/husk ratio. A sieberiana and Leucaena had the highest and lowest concentrations of condensed tannins respectively. The pods of A tortilis and A karoo were particularly rich in macro-and micro-minerals, while the others contained suf®cient quantities that could contribute substantially to the dietary requirements of small ruminants. The amino acid concentrations differed signi®cantly (p < 0.001) among the pods, with the Leucaena pods having the highest concentrations. The Leucaena pods and seeds also had higher (p < 0.001) lipid contents than the Acacia pods and seeds. Dry matter and nitrogen degradabilities were higher (p < 0.001) for the pods of A nilotica and A sieberiana, while A karoo had the lowest values. The cell wall constituents of the pods of A tortilis and A erioloba were the most and the least susceptible to microbial degradation respectively. The rates of degradation of the ®bre fractions as well as the lag times were similar (p > 0.05) among the pods. The results show that these pods can serve as a valuable source of nitrogen and minerals for ruminants fed roughage-based diets.

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