Growth and disappearance in a natural pasture under four levels of forage on offer

O experimento objetivou quantificar variáveis do complexo pastagem-animal para melhor manejo da pastagem. Houve quatro níveis de oferta (OF) de matéria seca (MS) – 4%, 8%, 12% e 16% do peso vivo (PV)/dia – para novilhos em pastejo contínuo durante a estação de crescimento 1990/91, num delineamento completamente casualizado, com duas repetições. Primavera e verão-outono constituíram as "épocas" para estudo. As OF promoveram resíduos de matéria seca em níveis médios de 432, 880, 1.300 e 1.878 kg/ha, respectivamente, que promoveram taxas de crescimento de comportamento linear positivo. Já o desaparecimento de MS foi curvilinear na primavera, e linear positivo no verão-outono, em relação às OF. A produção de MS apresentou resposta linear ao longo da estação de crescimento, com 2.512, 3.113, 3.786 e 4.053 kg/ha. A pastagem com OF 16% manteve a carga animal da primavera para o verão-outono (450 kg de PV/ha), enquanto nas menores ofertas a carga teve de ser diminuída de 800 para 498 kg de PV/ha na OF 4%, de 566 para 460 kg de PV/ha na OF 8%, e de 474 para 378 kg de PV/ha na OF 12%.The trial was conducted aiming at the evaluation of experimental variables related to the pasture-animal complex for a better management. There were four levels of forage dry matter on offer (FO) – namelly 4%, 8%, 12% and 16% of the liveweight per day – under continuous grazing, arranged in a completely randomized design with two replications. Spring and Summer-Autumn were considered as seasons for the study. The FO determined consistent levels of residual dry matter (DM) of 432, 880, 1,300 and 1,878 kg/ha, respectively, and its growth rates showed a positive linear relationship to FO levels. DM disappearance rates showed a curvilinear relationship to FO in spring and linear in Summer-Autumn and the dry matter production showed linear response (2,512, 3,113, 3,786 and 4,053 kg DM/ha) to FO levels. FO 16% maintained 450 kg LW/ha in both seasons; however, for the treatments with lower FO and lower residual DM/ha, the stocking rate declined as follows: from 800 to 498 kg LW/ha (FO 4%), from 566 to 460 kg LW/ha (FO 8%), and from 474 to 378 kg LW/ha (FO 12%)