Assessment of the nutritive value of Calliandra calothyrsus: in sacco degradation and in vitro gas production in the presence of Quebracho tannins with or without Browse Plus

The effects have been measured of the presence in the diet, of Quebracho tannins (QT) and Browse Plus (a commercial polyethylene glycol (PEG) preparation) on the rumen degradation and in vitro fermentation of samples of Calliandra calothyrsus leaf and stem from Zimbabwe. Four rumen environments were created by feeding four sheep with a grass hay, grass cubes and whole barley basal diet (Control), this diet incorporating 50 g QT kg−1 (CQT), or CQT supplemented with 0.1 g or 1.0 g (CQT + 0.1; CQT + 1.0) Browse Plus kg−1 diet. A 4 × 4 Latin square design was used with periods of 4 weeks. There were no differences (P > 0.05) in the potential degradation of Calliandra leaves in sacco in the sheep rumen between the four rumen environments. The QT significantly reduced (P < 0.05) the in sacco degradation of the stems. Browse plus at 1.0 g kg−1 significantly alleviated this effect of QT. Crude protein loss in the leaves of Calliandra was not affected by the presence of QT with or without Browse Plus. The CP loss at 48 h (54%) was close to the asymptote, and represented over 95% of the total CP lost in sacco in the rumen. For the stems, over 73% of the CP was released in 24 h. In incubations in rumen liquor in vitro, QT reduced the asymptote of gas production of both leaves and stems, and the presence of 1.0 g kg−1 Browse Plus was able to reverse most, but not all of the depression in gas production. Total VFA production was also reduced by QT in these incubations, and the treatments resulted in changes in the relative proportions of acidic fermentation products.