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7 páginas, 4 tablas., Finding alternatives to deal with the lack of feed during the dry period is a challenge for animal research in tropical areas. The effect of age of regrowth (60, 120 or 180 days), chemical composition and secondary metabolites on Leucaena leucocephala digestibility was evaluated. A randomized block design with six replicates was used. The statistical procedures included analysis of variance and correlation and regression analysis. Multiple linear equations between in vitro and in situ digestibility, as dependent variables, and the age of regrowth, NDF, ADF, lignin, Ca, Si, NDF/N, ADF/N, tannins, condensed tannins and saponins, as explanatory variables, were established. An increase in cell wall content and its components with age of regrowth, and a variable response in mineral concentrations were observed. The linear equations relating digestibility with the age of regrowth, NDF, ADF and Si (R2[0.78) or with the secondary metabolites tannins, condensed tannins and saponins (R2[ 0.79) were statistically significant (p\0.05) explaining a high proportion of variance. The regrowth age, cell wall components, polyphenol compounds, saponins contents determined the forage digestibility and these aspects must be taken into consideration to estimate the nutritional value of Leucaena roughage to be used as feedstuff for animals.

10 páginas, 4 tablas., This experiment has examined the effects of age of regrowth (60, 120 or 180 days) and season (dry or rainy period) on the nutritional quality of roughage from Erythrina variegata harvested in the Cauto Valley, Cuba. A randomized block design with three replicates was used. Proximate and mineral composition, in vitro and in situ dry matter digestibility were evaluated, in addition to the secondary metabolites (tannins, phenols, verbascose, stachyose, raffinose, flavonoids, triterpenes and steroids) at different ages of regrowth, in both seasons of the year. There was a significant interaction between treatments for most of the nutritional components or digestibility coefficients analyzed, although the pattern followed with age of regrowth was similar in both seasons. The gas production increased with the age of regrowth and the higher value was obtained during the dry season, while the lag phase was longer in the rainy season. The results of this study show the marked effect of climatic factors on the nutritive quality of E. variegata. In general, as maturity was increased the concentrations of secondary metabolites also increased, but only condensed tannins were close to the limits for which ruminal fermentations can be affected. All these aspects should be considered in this species when it is used in animal feeding.