Management strategies to reduce environmental impacts of beef cattle production systems

Abstract

This project aims to evaluate the efficiency of N fertilization and use of strategic supplementation on productivity, economic efficiency and environmental impacts of pasture based meat production systems. The project will last for five years and will be divided into two experiments. The experiments I and II will be conducted on Brachiaria brizantha cv. marandu pastures grazed by cattle using continuous stocking in the rearing phase and finishing phase in either pasture or feedlot. In Experiment I, treatments will consist of four levels of N fertilization (0, 90, 180 and 270 kg ha-1 year-1) split in three applications during the rainy season. In the second experiment, treatments will consist of four supplementation strategies for the grazing animals. In the first and second years these strategies will include mineral mix, supplement using energy from corn meal associate to cotton seed meal, supplement with 50% replacement of protein source by distiller's dried grains with solubles (DDGS), and supplement with 100% replacement of protein source by DDGS. In the third and fourth years the treatments will consist of mineral mix, supplement using energy from citrus pulp associate to cotton seed meal, supplement with 50% replacement of protein source by DDGS associated with citrus pulp, and supplement with 100% replacement of protein source by DDGS associated with citrus pulp. Environmental impacts to be assessed include nitrogen loss through volatilization of ammonia and nitrous oxide and CO2 and methane emission (Experiment I). Pasture evaluation will include herbage mass, herbage accumulation, apparent N recovery, efficiency of N utilization, and forage nutritive value. Animal response variables include intake and nutrient digestibility, enteric methane, ruminal parameters, performance, and carcass characteristics. Finally, the economic viability of pasture-based cattle production systems, including yearling stocker finished on pasture or feedlot will be evaluated. (AU)