Abstract: A 3-year experiment was conducted to determine pasture and cattle responses to tall fescue–endophyte association (free, novel, and wild endophyte associated with ‘Jesup’ cultivar) and fertilization source (inorganic and broiler litter). Fertilization source had only minor or no effects on botanical composition, forage mass, cattle stocking rate, and yearly cattle performance and productivity. However, cattle performance and production were greater with broiler litter than with inorganic fertilization during summer, but lower in autumn and winter, suggesting a difference in timing of nutrient availability to forage due to mineralization of organic nutrients in broiler litter. Pastures with wild endophyte association either had higher forage mass during some periods or were able to carry more cattle than other endophyte associations. Cattle performance was lower with wild than with other endophyte associations at all times of the year, except in summer. Cattle gain in winter was not different among endophyte associations (64kgha−1; p =0.43), was lower in spring with wild endophyte than with other endophyte associations (244kgha−1 versus 302kgha−1; p =0.04), was higher in summer with wild endophyte (147kgha−1 versus 117kgha−1; p <0.001), and was lower in autumn with wild endophyte (97kgha−1 versus 129kgha−1; p =0.10). Seasonal differences in pasture responses to fertilization and endophyte association suggested that management options could be developed to avoid or limit toxic cattle responses to wild endophyte. [Copyright &y& Elsevier]