Enteric fermentation has such a high impact on my beef/dairy carbon footprint. How is the YM determined?

Enteric fermentation has such a high impact on my beef/dairy carbon footprint. How is the YM determined?

 There are two feed approaches in the Cool Farm Tool: The first one allows to specify the dry matter intake for each feed item for each animal category, while the second requests the percentage of fresh matter intake for each feed item for the entire herd. The YM value is determined as the weighted average of the digestive efficiency of all feed items either for each animal category (feed approach 1) or the entire herd (feed approach 2).