Extensive comparisons of the effects of tropical shrub legumes rich in condensed tannins (CT) require well-conserved material. It is, however, unclear if the application of even gentle methods like freeze drying (lyophilization) affects the results in comparison to fresh material. Therefore, an experiment with the gas-pressure transducer technique, simulating ruminal fermentation dynamics in vitro, was conducted to investigate the effect of freeze drying on the ruminal nutrient degradability of three tropical multipurpose shrub legumes. Leaves of the CT shrubs Calliandra calothyrsus and Flemingia macrophylla and of the CT-free shrub Cratylia argentea were tested either in fresh form or lyophilized. In order to simulate practical feeding conditions, the legume leaves were incubated together with Brachiaria humidicola (1:2) for 144 h. Additionally, incubations were carried out either with or without polyethylene glycol (PEG) to be able to separate effects either dependent or independent of the CT. Only few differences were found between fresh and lyophilized leaves. These included that the proportion of apparently undegraded nitrogenous compounds was higher in fresh than in lyophilized leaves of Flemingia macrophylla, and freeze drying had a limited influence on volatile fatty acid production in Calliandra calothyrsus. The variables related to degradation dynamics (i.e., total gas production, the time until the point of inflection, apparent dry matter degradability), however, were not influenced. There was also no difference between CT and non-CT plants in that respect, as is also obvious from the lack of interactions of state of the plant material and PEG addition. This indicates that effects of freeze drying of shrub leaves on overall ruminal nutrient degradation in mixed grass-legume diets were minor.

A pot experiment was conducted to assess the fertiliser value of faeces from sheep fed with a diet supplemented with legumes free of or containing condensed tannins. Ten animals received the same five diets in different experimental runs of a double Latin Square design, all consisting of a low quality tropical grass ration, supplemented with 450g/kg legumes. Legume treatments were either solely Vigna unguiculata (a tannin free herbaceous legume) or mixtures of V. unguiculata with either Calliandra calothyrsus or Flemingia macrophylla (both shrub legumes rich in condensed tannins) in ratios of 2:1 and 1:2. Faeces from animals receiving the same diets were pooled and applied at two levels (20 and 80 mg N/kg soil) to pots with seedlings from the cultivar Mulato II, a Brachiaria grass hybrid. An acidic infertile tropical soil was used. Aerial biomass yield and plant N content were evaluated. The results seem to indicate that the N fertiliser value of faeces from sheep receiving a diet supplemented with tanniniferous legumes is not substantially reduced compared to diets free of condensed tannins. However, the data also indicate that nitrogen was not the most limiting element in the soil used since mineral fertilisation without extra nitrogen was efficient, too.