The Tier 2 predictive model is useful for estimating enteric methane emissions from dairy cattle at farm level in Spain
Abstract
Globally, animal agriculture is a major source of greenhouse gas (GHG) emissions. Various institutions such as the Intergovernmental Panel on Climate Change (IPCC), estimate that livestock accounts for 17% of global anthropogenic GHG emissions. In Spain, livestock farming, including enteric methane production, accounted for 9.1% of total greenhouse gas emissions in 2020. There are strategies to reduce their impact, such as improving the feeding and management of ruminants. When estimating GHGs, there are many methods to choose from, each aimed at getting accurate and precise results for the emissions of each livestock breeding. These methods improved over time, moving towards more advanced approaches. The selection of the methodology falls into two types: 1) methods based on observed emissions data; and 2) methods based on calculation procedures that include emission factors (EF). Indirect methods are the most suitable for measuring enteric methane emissions under on-farm conditions and with large numbers of animals. In this context and from a clinical point of view, the predictive equations developed by the International Panel of Climate Change (IPCC) in its various updates are emerging. The IPCC guidelines highlight the use of the Tier 2 approach focusing on the methane conversion factor (Ym, %) and gross energy (GE) of the ration for the calculation. There is a lack of studies on this subject in Spain, however, investigations using this view have been carried out in many countries. Consequently, it is not possible to determine how much enteric methane is produced by cattle and what possible corrective measures are adequate, according to the particularities of the Spanish agricultural sector.
This review aims to help veterinarians working on livestock farms assess enteric methane emissions, in close collaboration with nutritionists based on data provided by the IPCC. Only then will it be possible to identify the positive and negative aspects of each farm and look for nutritional options to reduce emissions without compromising farm productivity, while addressing environmental concerns.
