Fire management of natural grasslands and cattle productivity in the lower eastern plains of Colombia

The productivity and nutritive value of various natural grasslands of the lower eastern plains (Llanos) of Colombia, fire-managed annually during the dry season, were usually low. Annual biomass was 2-3.5 tons of dry matter (DM) per hectare and total crude protein content of fodder was 5-11% of DM depending on the season and phenological stage. Under traditional managing conditions (non-stop grazing, no fire or fire at the beginning of the dry season, stocking rate of 8-10 ha per animal), cattle weight gains were low during the rainy season (average daily weight gains between 150-300 g) and cattle usually lost weight during the dry season (150-250 g per day). During in-station experiments, significant differences in animal productivity were observed based on the botanical content and, even more so, on the pastoral value (a grassland value scale that combined productivity, nutritive value and desire of the animal for the species) of the natural grassland, which were determined by the soil texture (either sandy-clay or clay-silty). Regrowth occurred as a result of annual fires in the dry season. Nevertheless, the year after year repetition of these fires associated with free non-stop grazing negatively modified the flora. The authors tested two grassland-burning sequential systems in a set of parcels used in rotation. The systems allowed burning intervals of 16 months and provided the cattle with regrowths protected from grazing every four weeks. Even with an average annual stocking rate multiplied by two (4 ha per head), the individual weight gains of growing cattle were significantly improved without degrading the vegetation