Herbage Responses and Grazing Performance of Mature Horses in Warm-Season Perennial Grass–Legume Mixed Pastures

The pasture–animal interface of warm-season perennial grass–legume mixed pastures has never been investigated in forage-based equine systems. Therefore, this 2-year study investigated the herbage and animal responses under 84-day continuous stocking in mixed pastures of rhizoma peanut (RP, Arachis glabrata Benth) and bahiagrass (BG, Paspalum notatum Flüggé) with 30 kg nitrogen (N) ha−1 (BG-RP) compared to BG pastures fertilized with 120 kg N ha−1 (BG-N120) and no N (BG-N0). Measurements were taken every 14 days, except for intake and in vivo digestibility, which were measured every 28 days. BG-N120 had the highest stocking rate (p = 0.01; 3.7 AU ha−1) in 2019, while BG-N0 had the lowest (p = 0.01; 2.6 AU ha−1) in 2020. Crude protein and digestible energy were greatest (p < 0.05) for BG-N120 and BG-RP in some of the evaluation days in 2019 but similar across pastures in 2020. Crude protein digestibility was greatest (p < 0.05) for BG-RP in the late season. Intake was less (p = 0.03) for horses grazing BG-RP (3.2%BW) compared to BG-N0 (5.0%BW). Nonetheless, no differences (p > 0.05) were observed among pastures for body measurements. The results indicate that BG-RP pastures can improve forage nutritive value and maintain horse body condition while maintaining similar stocking rate to monoculture bahiagrass with high N fertilizer rates.