Strategic combination of nutritional tools for enteric and manure methane emissions mitigation in cattle: synergistic and additive responses

Abstract

The accumulation of greenhouse gases (GHG) in the atmosphere remains an important topic of scientific and public interest around the world. The increase in these gases has been considered as a major cause of global warming. Among the greenhouse gases, methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) are the most important in the context of agricultural activity. In this context, the national agriculture, especially the Brazilian livestock production, has been the target of numerous criticisms related to global warming, this is because in Brazil cattle represents 83.9% of all livestock production and, on the other hand, the country has the second largest cattle herd in the world. Manipulation of ruminal fermentation, aiming to reduce GHG emissions, can be achieved through nutritional strategies. However, for this, researchers in this area should consider that methane production is directly proportional to the concentration of dissolved H2, being therefore one point that still needs to be worked in order to direct the dissolved H2 to production processes, thus avoiding energy losses through the enteric methane production and, consequently, waste from ruminants. Therefore, this project aims to evaluate the interaction between different nutritional strategies, feed additives and supplements (additives cocktail), as manipulators of ruminal kinetics, fermentation parameters, and ruminal microbiota. Similarly, the aim is the evaluation of different nutritional strategies for the mitigation of methane emissions via enteric fermentation determined by ex-situ technique (micro-rumen) of methane measurement. Five experiments and five sub-experiments make up this research project. It will be evaluated the ingestive (dry matter intake and feeding behavior) and digestive parameters (total apparent digestibility and nutrient excretion), ruminal kinetics (passage, digestion and disappearance rate), ruminal fermentation (short chain fatty acids, methane, ruminal pH and ammonia nitrogen), protozoa and archaea population in the rumen, as well as nitrogen balance. The CH4 production and short chain fatty acids (SCFA) will be determined by the ex-situ technique. The concomitant measurement of methane production and the main ruminal fermentation parameters will assist on the estimation of Relative Energy Loss (REL). Additionally, this project will evaluate the production of CH4, N2O, and CO2 in the feces of animals with the aid of digesters made for this purpose. It is expected that the interactions among different nutritional tools will present synergistic (also known as potentiation) or at least additive effects in the reduction of greenhouse gases emission by ruminants. (AU)