this study aimed to evaluate the effect of simulated chewing in the laboratory on the survival of seeds of four tropical forage legumes (butterfly pea, clitorea ternatea; estilosantes, stylosanthes capitata/s. macrocephala 'campo grande; archer, macrotyloma axillare and perennial soybean, neonotonia wightii) submitted to different periods of acid enzymatic digestion in vitro. three trials were conducted to observe the percentage of destroyed seeds by the mastication; to compare the germination of the seeds (intact seeds, simulated mastication, scarification with sandpaper, mastication and scarification with sandpaper). and, finally the seeds were incubated at 39oc with hydrochloric acid and pepsin for: 0, 2, 4, 8, 12 and 24 hours. the percentages of not destroyed seeds in mastication (archer, 91,5; perennial soybean, 88.0; butterfly pea, 82.1, and estilo, 81.1), associated with the beneficial effects of scarification on germination (64.7, 60.0, 92.0 e 87.3%, respectively) and the effects of time of acid-enzymatic digestion (75% higher if they stay 24 hours in hcl + pepsin) associated to the hard and not permeable coats of legume seeds, allow a high potential for resistance, and to pass intact through the digestive tract of cattle, being able to germinate when defecated in the pastures. however, estilo should not be included in the feeding of cattle for this purpose, because it do not resists the acid-enzyme digestion.