Comparative meta-analysis of nitrogen partitioning in grazing dairy cattle consuming tropical and temperate forages

• Grant number: 25/24223-6
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: February 01, 2026
• End date: May 31, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Vinícius Carneiro de Souza
• Grantee: Stella Zanini Barbosa
• Supervisor: Amelia Katiane de Almeida
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Institution abroad: Massey University, New Zealand
• Associated to the scholarship: 25/07543-7 - Models for predicting nitrogen excretion in dairy cattle, BP.IC

Abstract

Livestock farming is one of the primary sectors responsible for greenhouse gas (GHG) emissions, particularly enteric methane and nitrous oxide from manure management and urine deposition in the soil. Given the growing global demand for meat and animal products, there is an urgent need to discuss the environmental impacts of the activity and seek sustainable alternatives. Dairy cattle, in particular, exhibit low nitrogen use efficiency (NUE), resulting in significant contributions to N losses and GHG emissions. Factors such as diet type, climatic conditions, and pasture composition directly influence the partitioning of nitrogen between retention, fecal excretion, and urinary excretion. In the Brazilian context, characterized by a tropical climate, the predominant forage species generally have lower nutritional quality compared to grasses in temperate climates, which tends to reduce NUE. Despite advances achieved in countries with temperate climates, significant gaps still exist in understanding the metabolism of nitrogen and carbon in tropical systems. New Zealand, a benchmark in studies on emissions from grazing animals, has advanced infrastructure and technology for measuring CH4 and N2O. Thus, this project proposes an international collaboration aimed at enhancing methodologies applicable to the tropical context, with the goal of increasing the accuracy of emission estimates and guiding public policies for mitigation in sustainable agriculture.