The effect of drying treatment on the fodder quality and tannin content oftwo provenances of Calliandra calothyrsus Meissner

The effects of freeze drying and of air drying at 30 degrees C on the nutri tive value of Calliandra calothyrsus leaves were evaluated, using material from two provenances grown together under controlled greenhouse conditions. Freshly harvested leaf of each provenance was compared with the dried trea tments In terms of in vitro digestibility, content of extractable, protein- bound and fibre-bound proanthocyanidin (condensed tannin) and protein preci pitation activity of the extractable fraction, as well as crude protein and fibre content. The effect of long-term (12 months) storage of fresh-frozen and dried leaf was also evaluated. Provenance was found to have a major ef fect on most of the traits, and large differences between the provenances i n proanthocyanidin structure were found by high-performance liquid chromato graphy, with the tannins of one provenance consisting mainly of catechin/ep icatechin subunits (producing cyanidin on treatment with butanol/HCl), and those of the other mainly gallocatechin/epigallocatechin subunits (producin g delphinidin with butanol/HCl). This also resulted in large differences in colour yield in the butanol/HCl assay for proanthocyanidins, necessitating separate standards for each provenance. Both drying treatments tended to i ncrease digestibility, though the effect was only significant for one prove nance. Air drying, but not freeze drying, increased proanthocyanidin bindin g to protein, but not to fibre, in both provenances. Long-term freezing red uced proanthocyanidin content by about half and should be avoided in tannin research. The study suggests that careful air drying, without excessive he ating, may not reduce the nutritive value of C calothyrsus, though this nee ds validation through feeding studies with ruminants. (C) 2000 Society of C hemical industry.