Evaluation of selected forage legume species under dry season grazing in subhumid Nigeria

Legume pastures (fodder banks), based primarily on Stylosanthes hamata cv. Verano, were developed for the subhumid zone of West Africa to alleviate the dry season nutritional constraints to livestock production. A three-year grazing trial (1990-1993) was conducted to compare the performance of Centrosema pascuorum Mart. ex Benth (Centurion) cv. Cavalcade or Chamaecrista rotundifolia (Pers.) Grenne cv. Wynn cv. Wynn with Stylosanthes hamata (L.) Taub. cv. Verano.;Plant establishment, regeneration, dry matter yield, botanical composition, crude protein and in-vitro digestibility of pastures were monitored. Performance and grazing behavior of heifers when supplemented with the three legumes during the dry season was compared with native pastures. Responses of the legumes to inoculation with rhizobia were also assessed.;Both S. hamata and C. rotundifolia persisted as major pasture components under grazing for the duration of the study, while C. pascuorum failed to survive beyond the second growing season. Whole plant crude protein content was generally higher for sown legumes than grasses and forbs at the beginning of the dry season, however, it dropped below the critical (7%) level over half of the dry season during the first and second years.;Higher animal performance was recorded in legume pastures compared to native pastures. Mean seasonal cumulative liveweight losses increased for all treatments from the first year to the third year. Seasonal cumulative liveweight losses of heifers on legume pastures were not significantly different in the first two years. During the final year, however, there was a greater rate of liveweight loss in C. pascuorum pastures.;Heifers spent a higher percentage of time grazing and less time walking in legume treatments compared to native pastures. Outside the supplemental pastures, lowest contributions of the range forage, crop residue and browse to total grazing resources were recorded in March, which suggests a critical period in the dry season. Lack of sufficient amounts of forage as well as reduced quality contributed to these losses.;Both C. pascuorum and C. rotundifolia responded to the rhizobial inoculation with commercial inoculum, while it did not show any improvement over the native rhizobia for S. hamata.