The rumen digestion of dry matter, nitrogen and cell wall constituents of the pods of Leucaena leucocephala and some Acacia species

The disappearance of dry matter (DM), nitrogen and cell wan 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(-1) DM. The Leucaena pods and seeds had higher (p > 0.001) CP contents than the Acacia pods and seeds. The neutral detergent fibre 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 influenced 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 sufficient quantities that could contribute substantially to the dietary requirements of small ruminants. The amino acid concentrations differed significantly (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 fibre 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. (C) 2001 Society of Chemical Industry.