Nutritive Evaluation of Nitrogenous Fractions in Leaves of Gliricidia sepium and Caliandra calothyrsus in Relation to Tannin Content and Protein Degradation by Rumen Microbes in Vitro

A study of two fodder tree species, Gliricidia sepium and Caliandra calothyrsus, was undertaken to investigate the degradation of leaf protein (crude and soluble protein) by rumen microbes during in vitro fermentation and the effect of total tannin content on that degradation. Differences in DMD and protein degradation were observed between the two leaf species. C. calothyrsus, after extraction with 70% acetone, showed greater DMD and crude protein losses, 40% and 20% greater, respectively. The cumulative gas production of C. calothyrsus was increased after extraction with 70% acetone. It was concluded that the differences in protein degradation characteristics were mainly due to the inhibitory effects of tannins. The apparent increased resistance of glycoproteins to degradation appeared to be of relatively minor importance to the nutritive value of the fodder. Keywords: Protein degradation; tree leaf; rumen culture; in vitro DMD; tannins; glycoproteins