| rees and shrubs are attractive sources of protein as feed or diets for livestock in the tropics. However, many of these unconventional feeds contain condensed tannins and other secondary compounds that can reduce protein and fiber digestibility. The objectives of this study were to improve chemical and biological assays for condensed tannins in tropical forages.;Neutral detergent appeared to remove other nontannin compounds from Centrosema, Clitoria, Erythrina and Pueraria, resulting in increased digestibility of isolated NDF. Removal of ND solubles resulted in smaller increases of digestibility in tannin-containing species such as Desmodium. This indicates that curve subtraction for fractional gas production from many tropical forages is not valid, and also suggests that the value of the ND solubles in tropical forages is inferior and overestimated.;The levels of condensed tannins in samples from Arachis, Desmodium, Gliricidia and Manihot were estimated using individual standards in the acid butanol assay. The standards were purified by precipitation with ytterbium acetate. The biological activity of condensed tannins in these plant species was evaluated by determining their ability to precipitate alfalfa leaf protein. The BSA radial diffusion method was modified using a plant protein source and a pH of 6.8 to more closely represent ruminal conditions. The ratio of protein to tannin in precipitates vary widely according to plant source. Also concentrations of BSA and alfalfa leaf protein caused major differences in precipitating ability. Alfalfa protein appeared to be more representative in characterizing the respective precipitating ability of tannins. The ability of tannins to precipitate plant protein was not related to tannin concentration. The condensed tannin content in descending order was... |
