Why measuring feed efficiency is difficultIn dairy cattle, feed efficiency (FE) is most often expressed as residual feed intake (RFI), which is the difference between a cow’s actual feed intake and the amount predicted from her milk production, metabolic body weight and body weight change. However, RFI depends on accurate daily feed intake data for individual cows, which is a major hurdle on commercial dairy operations. In respiration chamber (RC) studies, CO₂ production has been shown to accurately predict HP, which is closely tied to feed energy utilization. An advantage of GreenFeed system in estimating feed efficiency is that feed intake and analysis are not needed. ConclusionsThe Finnish study demonstrates that GreenFeed systems can reliably estimate feed efficiency in dairy cows using gas exchange data, with results comparable to gold-standard respiration chambers.