Prediction of Individual- and Herd-Level Methane Emissions From Enteric Fermentation in Holstein Heifers

Several prediction equations for methane (CH₄) emissions from enteric fermentation in cattle have been proposed for individual-level prediction using the breath CH₄ to carbon dioxide (CO₂) concentration ratio and for herd-level prediction using animal and/or feed information, owing to the difficulty of measuring CH₄ emissions. In dairy cattle, most equations have been developed for lactating cows and are restricted for heifers, whose physiological status and diets differ from those of lactating cows. The present study developed prediction equations for CH₄ emissions from dairy heifers using variables readily obtainable on farms. Equations were developed by fitting a linear regression model including metabolic body weight (MBW), dry matter intake (DMI), estimated daily gain (DG), metabolizable energy intake-to-DMI ratio, and/or the CH₄:CO₂ emission ratio as explanatory variables. Data were collected using respiration chambers (n = 103; mean age, 13.0 months; mean body weight, 312 kg). The best-performing models for both individual- and herd-level prediction included MBW and DMI as explanatory variables. Replacing DMI with estimated DG resulted in only a slight reduction in model performance. Consequently, the developed equations offer flexible applications on farms based on data availability.