17 S. Albores-Moreno J. A. Alayón-Gamboa L. A. Miranda-Romero G. Jiménez-Ferrer J. C. Ku-Vera L. Vargas- Villamil Journal of Animal and Plant Sciences JAPS 20182018/10/01 28 5 1263-1275 1018-7081 NA Study conducted to know the nutritional composition, in vitro degradation and the potential fermentation of tree leaves species grazed by ruminants in secondary vegetation of a deciduous forest. Tree leaves were selected from 18 tree species that were subjected to in vitro fermentation. Fermentation variables were analyzed with a designed block repeated over time. The content of CP, NDF and ADF fluctuated among species, from 109 to 262, 391 to 641 and 322 to -1 579 g kg of DM, respectively. The concentrations of condensed tannins (CT) presented a wide variation among species -1 and ranged from 1.73 to 233.45 g kg DM. The significant differences ( P <0.05) observed among species in fermentation and digestibility. G. floribundum, M. lindeniana, V. gaumeri, H. barvensis, T. amygdalifolia and C. -1 -1 gaumeri had the highest gas volume (155 to 293.88 mL g ), total fermentation (379.45 to 677.39 mg g ), fermentation -1 -1 rate (0.031 to 0.038 h ), and soluble fraction (178.3 to 265 g kg of DM ). In addition, they had highest values of the -1 -1 rapid fermentation fractions (123.58 a 214.88 mg g ), medium fermentation (37.07 to 217.87 mg g ), and slow -1 fermentation fractions (162.33 to 244.64 mg g ), and the highest IVDMD values ( 39.71 to 54.93%) and IVOMD (4 7.96 to 66.50%). The species H. albicans, P. piscipula, B. divaricata, L. rugosus, N. emarginata and M. bahamensis had the -1 lowest potential fermented gas emission index ( 181.13, 181.19, 200.59, 206.36 and 217.24 mL g MOD). It is concluded that the species G. floribundum, M. lindeniana, V. gaumeri, H. barvensis, T. amygdalifolia and C. gaumeri present in the secondary vegetation of the forest have a good potential in the feeding of ruminants due to their highest fermentability in the rumen. a high diversity of plant species that is used in multiple IVOMD, fermentation kinetics, tree leaves, secondary metabolites. Pakistan Agricultural Scientists Forum https://thejaps.org.pk/AbstractView.aspx?mid=2018-JAPS-506