Stable isotopes in the determination of greenhouse gases from integrated systems: in vivo and in vitro approaches

• Grant number: 24/06301-7
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: June 01, 2024
• End date: May 31, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Pastures and Forage Crops
• Principal Investigator: Adibe Luiz Abdalla
• Grantee: Thaynã Gonçalves Timm
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 21/10573-4 - Center for Carbon Research in Tropical Agriculture (CCARBON), AP.CEPID

Abstract

The research project aims to assess the in vitro production of enteric methane (CH4) from substrates containing biomass suitable for ruminant grazing, incorporating legumes, tropical macroalgae, and biochar. It seeks to evaluate both short and long-term contributions to CH4 emissions, isotopic compositions, and impact on the rumen microbiome. Experiments will be conducted at LANA-CENA/USP to analyze differences in isotopic composition between various biomass sources used as ruminant feed. Trials will encompass in vitro and in vivo conditions to systematically assess the specific contribution of these biomasses to CH4 production. Isotopic composition of CH4 will serve as a critical metric in this evaluation, aiming to advance understanding of their influence on CH4 emissions. Substrates will undergo incubation in glass bottles with buffer solution and inoculum. Gas production and CH4 concentration will be measured, followed by treatment of undegraded substrate to estimate microbial mass production. Trials will simulate ruminal fermentation conditions over 21 days, including adaptation, intermediate, and stable phases. Parameters like dry matter and organic matter degradability will be quantified, along with fermentation effluent analysis for pH, short-chain fatty acids, ammonia, and ruminal microbiota studies. Samples will undergo analysis for isotopic compositions of carbon (13C) in food, residual undegraded material, and gases. Proportions of different plants in CH4 will be estimated, and carbon isotopic composition of gases will be determined using a cavity ring-down spectrometer. Effluent samples will be collected for DNA extraction and Real-time PCR analysis to quantify specific genes related to rumen microorganisms, including bacteria, protozoa, fungi, and functional marker genes. A database (BDD) will be developed containing information on organic matter degradability, CH4 production, short-chain fatty acids, and gene copy numbers. Descriptive and multivariate analyses will be performed to understand the influence of various variables on methane emission and rumen microbiota. Statistical tests including Welch's t-test and Tukey test will be used for comparisons. This project aims to contribute valuable insights into mitigating methane emissions in ruminant production systems and understanding their impact on rumen microbiota dynamics. (AU)