Nutritional assessment of tropical pastures as a sustainability strategy in dual-purpose cattle ranching in the South of Lake Maracaibo, Venezuela

Abstract

Pastures represent the greatest sustainability challenge for tropical cattle, as they are fibrous pastures, low in protein, with few soluble carbohydrates and limited digestibility. To evaluate the nutritional quality of tropical pastures, during the rainy and dry season a farm dedicated to raising dual-purpose cattle in the South of Lake Maracaibo-Venezuela was visited; there, six paddocks dominated by grasses adapted to the ecological conditions of the tropical humid rainforest were randomly selected. The sampling consisted of collecting, simulating the selective biting pattern of the animal, all the forage biomass found in 1 m 2 delimited by a metal frame that was thrown on several occasions until covering the grazing area. A final composite sample was made for each paddock, which were weighed and analyzed to determine parameters of nutritional interest. The study revealed that the paddock as a source of variation affected (P < 0.05) the floristic composition of the pastures, while the highest yield of consumable green matter, dry matter, crude protein, ether extract, ash and nitrogen-free extract was recorded during the rainy season (P < 0.05); however, there was no significant effect (P > 0.05) of the season on the content of total digestible nutrients, neutral detergent fiber and acid detergent fiber. The results suggest intensifying grazing during the wettest season and incorporating a gradual fertilization plan that guarantees higher forage biomass during the drought.